Bump platform from 3.1.1 to 3.1.2 in /app_dart (#3023)

Bumps [platform](https://github.com/flutter/packages/tree/main/packages) from 3.1.1 to 3.1.2.
<details>
<summary>Commits</summary>
<ul>
<li><a href="https://github.com/flutter/packages/commit/b4985e25fe0763ece3cfd7af58e0e8c9b9f04fc4"><code>b4985e2</code></a> [all] Add topics to pubspecs (<a href="https://github.com/flutter/packages/tree/main/packages/issues/4771">#4771</a>)</li>
<li><a href="https://github.com/flutter/packages/commit/961d161b5341e4c7c826d4740afe198004387866"><code>961d161</code></a> Fixed AlertDialog Height of example in image_picker (<a href="https://github.com/flutter/packages/tree/main/packages/issues/4800">#4800</a>)</li>
<li><a href="https://github.com/flutter/packages/commit/d7d3150e596686c9769249d7b0910ff6f9f5ee3b"><code>d7d3150</code></a> [rfw] Implement /* block comments */ in the text format (<a href="https://github.com/flutter/packages/tree/main/packages/issues/4769">#4769</a>)</li>
<li><a href="https://github.com/flutter/packages/commit/d55f26db4f1f4d9a05d3e45ed78aadf062c5036a"><code>d55f26d</code></a> [pigeon]: Bump org.jetbrains.kotlin:kotlin-gradle-plugin from 1.9.0 to 1.9.10...</li>
<li><a href="https://github.com/flutter/packages/commit/7cbde90c82679695180f4ccf70aedb673d622921"><code>7cbde90</code></a> Fix  popping repeated pages unexpectedly (<a href="https://github.com/flutter/packages/tree/main/packages/issues/4763">#4763</a>)</li>
<li><a href="https://github.com/flutter/packages/commit/94ba82ce52946395bba49cc3e11f47c84eb43213"><code>94ba82c</code></a> [pigeon] primitive enums (<a href="https://github.com/flutter/packages/tree/main/packages/issues/4580">#4580</a>)</li>
<li><a href="https://github.com/flutter/packages/commit/6a281dbcde15e2aa77c93dd93dd37f3bd7cbc40e"><code>6a281db</code></a> [css_colors] docs: Update deprecated link address (<a href="https://github.com/flutter/packages/tree/main/packages/issues/4537">#4537</a>)</li>
<li><a href="https://github.com/flutter/packages/commit/383bffa3991d6397eb4a00fb6f7f09f897252143"><code>383bffa</code></a> [google_maps_flutter] cloud-based map styling implementation (<a href="https://github.com/flutter/packages/tree/main/packages/issues/4638">#4638</a>)</li>
<li><a href="https://github.com/flutter/packages/commit/32460c7da3cf4ff01595706f29bec1317748bcdb"><code>32460c7</code></a> [image_picker] Fix exception when canceling <code>pickMultipleMedia</code> on iOS (<a href="https://github.com/flutter/packages/tree/main/packages/issues/4761">#4761</a>)</li>
<li><a href="https://github.com/flutter/packages/commit/3060b1aec99c54165fde27c1c8a58c553b657447"><code>3060b1a</code></a> [rfw] Support web (as JS) (<a href="https://github.com/flutter/packages/tree/main/packages/issues/4650">#4650</a>)</li>
<li>Additional commits viewable in <a href="https://github.com/flutter/packages/commits/platform-v3.1.2/packages">compare view</a></li>
</ul>
</details>
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</details>

app_dart/pubspec.yaml

@@ -48,7 +48,7 @@ dev_dependencies:
   flutter_lints: 2.0.3
   json_serializable: 6.7.1
   mockito: 5.4.2
-  platform: 3.1.1
+  platform: 3.1.2
   test: 1.24.6
 
 builders: