niv motoko-base: update 2e14c172 -> a7177e88 (#4273)

## Changelog for motoko-base:
Branch: next-moc
Commits: [dfinity/motoko-base@2e14c172...a7177e88](dfinity/motoko-base@2e14c17...a7177e8)

* [`a7177e88`](dfinity/motoko-base@a7177e8) enable multi-memory, bulk-memory on wasmtime ([dfinity/motoko-base⁠#593](https://togithub.com/dfinity/motoko-base/issues/593))

nix/sources.json

@@ -76,10 +76,10 @@
         "homepage": null,
         "owner": "dfinity",
         "repo": "motoko-base",
-        "rev": "2e14c17241ab5a49cecfb97ffdae6e7cff7ae9b7",
-        "sha256": "1xjqk490bzv66m18cj7p7hrvf9ry13wzsaif6sqmgzha4k1kbxls",
+        "rev": "a7177e88d0305683c3dbde410be2bf709113b721",
+        "sha256": "0bpr5h3s0r6y2gcvq2l7s29by9jz5z9x9akkn1j4ladq7q41j9cm",
         "type": "tarball",
-        "url": "https://github.com/dfinity/motoko-base/archive/2e14c17241ab5a49cecfb97ffdae6e7cff7ae9b7.tar.gz",
+        "url": "https://github.com/dfinity/motoko-base/archive/a7177e88d0305683c3dbde410be2bf709113b721.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
     "motoko-matchers": {