chore: don't test on webkit

GitHub actions doesn't support testing on webkit by default,
and it isn't worth investing the time now to investigate how
so just disable WebKit tests instead.

See #43

crates/dwn-rs-wasm/web-test-runner.config.mjs

@@ -18,7 +18,6 @@ export default {
   browsers: [
     playwrightLauncher({ product: "chromium" }),
     playwrightLauncher({ product: "firefox" }),
-    playwrightLauncher({ product: "webkit" }),
   ],
   nodeResolve: true,
   testFramework: "mocha",