Bump webpack in /glean/tests/unit/platform/utils/webext/sample

Bumps [webpack](https://github.com/webpack/webpack) from 5.64.0 to 5.64.2.
- [Release notes](https://github.com/webpack/webpack/releases)
- [Commits](webpack/webpack@v5.64.0...v5.64.2)

---
updated-dependencies:
- dependency-name: webpack
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

glean/tests/unit/platform/utils/webext/sample/package-lock.json

@@ -12,7 +12,7 @@
   "license": "MPL-2.0",
   "devDependencies": {
     "web-ext": "^6.5.0",
-    "webpack": "^5.64.0",
+    "webpack": "^5.64.2",
     "webpack-cli": "^4.9.1"
   }
 }