chore(deps): Bump rustls from 0.21.7 to 0.21.8 (#967)

Bumps [rustls](https://github.com/rustls/rustls) from 0.21.7 to 0.21.8.
<details>
<summary>Release notes</summary>
<p><em>Sourced from <a
href="https://github.com/rustls/rustls/releases">rustls's
releases</a>.</em></p>
<blockquote>
<h2>0.21.8</h2>
<ul>
<li>Fixes <code>ConnectionCommon::complete_io()</code> to flush writers
before potentially expecting a response.</li>
<li>Upgrades <code>*ring*</code> to 0.17 - <strong>Note</strong>:
<code>*ring*</code> 0.17 when built with <code>gcc</code> will
experience slower X25519 and Ed25519 operations compared to previous
releases.</li>
<li>Upgrades <code>rustls-webpki</code> to 0.101.7 to match
<code>*ring*</code> 0.17 dependency</li>
<li><code>Tls12CipherSuite::hash_algorithm()</code> and
<code>Tls13CipherSuite::hash_algorithm()</code> are now crate-internal.
This is a small breaking change to remove unintended exposure of
underlying <code>*ring*</code> types in the public API.</li>
</ul>
<h2>What's Changed</h2>
<ul>
<li>fuzz: remove unused webpki dependency by <a
href="https://github.com/ctz"><code>@​ctz</code></a> in <a
href="https://redirect.github.com/rustls/rustls/pull/1523">rustls/rustls#1523</a></li>
<li>Fix nightly clippy warning by <a
href="https://github.com/djc"><code>@​djc</code></a> in <a
href="https://redirect.github.com/rustls/rustls/pull/1443">rustls/rustls#1443</a></li>
<li>Upgrade to ring 0.17 by <a
href="https://github.com/djc"><code>@​djc</code></a> in <a
href="https://redirect.github.com/rustls/rustls/pull/1508">rustls/rustls#1508</a></li>
<li>Bump MSRV to 1.61 by <a
href="https://github.com/djc"><code>@​djc</code></a> in <a
href="https://redirect.github.com/rustls/rustls/pull/1516">rustls/rustls#1516</a></li>
<li>docs: adjust <em>ring</em> platform compatibility by <a
href="https://github.com/cpu"><code>@​cpu</code></a> in <a
href="https://redirect.github.com/rustls/rustls/pull/1532">rustls/rustls#1532</a></li>
<li>Fix: flush writers before potentially expecting a response by <a
href="https://github.com/robsdedude"><code>@​robsdedude</code></a> in <a
href="https://redirect.github.com/rustls/rustls/pull/1542">rustls/rustls#1542</a></li>
<li>v0.21.8 preparation by <a
href="https://github.com/cpu"><code>@​cpu</code></a> in <a
href="https://redirect.github.com/rustls/rustls/pull/1525">rustls/rustls#1525</a></li>
</ul>
<p><strong>Full Changelog</strong>: <a
href="https://github.com/rustls/rustls/compare/v/0.21.7...v/0.21.8">https://github.com/rustls/rustls/compare/v/0.21.7...v/0.21.8</a></p>
</blockquote>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/rustls/rustls/commit/c34477a068b340473dd654d1b25d6fac71e0c570"><code>c34477a</code></a>
Cargo: 0.21.7 -&gt; 0.21.8</li>
<li><a
href="https://github.com/rustls/rustls/commit/8cf2594dcb0fa523a1c62dbca279e3d4a41b8372"><code>8cf2594</code></a>
sign: fix clippy get-first warning</li>
<li><a
href="https://github.com/rustls/rustls/commit/ecc6cded2a1f2ada0884c62d642a90ce17d77964"><code>ecc6cde</code></a>
Flush writers before potentially expecting a response</li>
<li><a
href="https://github.com/rustls/rustls/commit/53adb9d2eb68034c1710e736f2dc343bbea657fb"><code>53adb9d</code></a>
docs: adjust <em>ring</em> platform compatibility</li>
<li><a
href="https://github.com/rustls/rustls/commit/d5d62499f2c4df9c6303eed51c730c8d031ec661"><code>d5d6249</code></a>
upgrade to ring 0.17</li>
<li><a
href="https://github.com/rustls/rustls/commit/a659652de0d813b362d401d7e58562bb5a15da3e"><code>a659652</code></a>
tls12/tls13: make hash_algorithm crate internal</li>
<li><a
href="https://github.com/rustls/rustls/commit/3ed39adc3d491fcd8635f425e4f58a903abca81f"><code>3ed39ad</code></a>
upgrade to webpki 0.101.7</li>
<li><a
href="https://github.com/rustls/rustls/commit/3e4a72e396554ef9479539d896e31afcb6bd4cd0"><code>3e4a72e</code></a>
Docstrings on expressions are not a thing</li>
<li><a
href="https://github.com/rustls/rustls/commit/e26d1d82aeda622e4166a2563f50af0a11067a29"><code>e26d1d8</code></a>
Bump MSRV to 1.61</li>
<li><a
href="https://github.com/rustls/rustls/commit/ab7b0e7a4fe2597b01d292ba3c4ba3819da22745"><code>ab7b0e7</code></a>
Drop rust-version metadata for internal crates</li>
<li>Additional commits viewable in <a
href="https://github.com/rustls/rustls/compare/v/0.21.7...v/0.21.8">compare
view</a></li>
</ul>
</details>
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