Bump actions/cache from 2.1.5 to 2.1.6

Bumps [actions/cache](https://github.com/actions/cache) from 2.1.5 to 2.1.6.
<details>
<summary>Release notes</summary>
<p><em>Sourced from <a href="https://github.com/actions/cache/releases">actions/cache's releases</a>.</em></p>
<blockquote>
<h2>v2.1.6</h2>
<ul>
<li>Catch unhandled &quot;bad file descriptor&quot; errors that sometimes occurs when the cache server returns non-successful response (<a href="https://github-redirect.dependabot.com/actions/cache/pull/596">actions/cache#596</a>)</li>
</ul>
</blockquote>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a href="https://github.com/actions/cache/commit/c64c572235d810460d0d6876e9c705ad5002b353"><code>c64c572</code></a> Catch and log unhandled exceptions stemming from closed file descriptor (<a href="https://github-redirect.dependabot.com/actions/cache/issues/596">#596</a>)</li>
<li><a href="https://github.com/actions/cache/commit/cc2d767a726ddd654506e76169ec14b20dc75915"><code>cc2d767</code></a> Update Rust directories recommended for caching (<a href="https://github-redirect.dependabot.com/actions/cache/issues/433">#433</a>)</li>
<li><a href="https://github.com/actions/cache/commit/2fa955d825a29821e73ec064792122ea9f70e573"><code>2fa955d</code></a> Update examples.md (<a href="https://github-redirect.dependabot.com/actions/cache/issues/588">#588</a>)</li>
<li><a href="https://github.com/actions/cache/commit/3a696372f2ec10535e4c026a4fdae5fcca629e4a"><code>3a69637</code></a> elixir typo - stray parenthesis (<a href="https://github-redirect.dependabot.com/actions/cache/issues/569">#569</a>)</li>
<li><a href="https://github.com/actions/cache/commit/366e5ba0224e0ebd6fba2a453d108cb20e734946"><code>366e5ba</code></a> Update cache key for Elixir (<a href="https://github-redirect.dependabot.com/actions/cache/issues/568">#568</a>)</li>
<li><a href="https://github.com/actions/cache/commit/8d3f2fc3ce25d6c95a1297ce8d93f9c3c3ac8f00"><code>8d3f2fc</code></a> Update dependencies (<a href="https://github-redirect.dependabot.com/actions/cache/issues/565">#565</a>)</li>
<li>See full diff in <a href="https://github.com/actions/cache/compare/v2.1.5...v2.1.6">compare view</a></li>
</ul>
</details>
<br />

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</details>

Fixes #1107

COPYBARA_INTEGRATE_REVIEW=#1107 from google:dependabot/github_actions/actions/cache-2.1.6 d41e247
PiperOrigin-RevId: 376626348

.github/workflows/ci.yml

@@ -24,7 +24,7 @@ jobs:
       - name: 'Check out repository'
         uses: actions/checkout@v2.3.4
       - name: 'Cache local Maven repository'
-        uses: actions/cache@v2.1.5
+        uses: actions/cache@v2.1.6
         with:
           path: ~/.m2/repository
           key: maven-${{ hashFiles('**/pom.xml') }}
@@ -51,7 +51,7 @@ jobs:
       - name: 'Check out repository'
         uses: actions/checkout@v2.3.4
       - name: 'Cache local Maven repository'
-        uses: actions/cache@v2.1.5
+        uses: actions/cache@v2.1.6
         with:
           path: ~/.m2/repository
           key: maven-${{ hashFiles('**/pom.xml') }}
@@ -80,7 +80,7 @@ jobs:
       - name: 'Check out repository'
         uses: actions/checkout@v2.3.4
       - name: 'Cache local Maven repository'
-        uses: actions/cache@v2.1.5
+        uses: actions/cache@v2.1.6
         with:
           path: ~/.m2/repository
           key: maven-${{ hashFiles('**/pom.xml') }}