[CQ] studio-contribs XML cleanup (#8158)

* Suppresses `PluginXmlI18n` where we'll never internationalize.
* Removes a redundant `serviceInterface` declaration.
* (Also: removes an unused import.)

---

- [x] I’ve reviewed the contributor guide and applied the relevant
portions to this PR.

<details>
  <summary>Contribution guidelines:</summary><br>

- See our [contributor
guide]([https://github.com/dart-lang/sdk/blob/main/CONTRIBUTING.md](https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview)
for general expectations for PRs.
- Larger or significant changes should be discussed in an issue before
creating a PR.
- Dart contributions to our repos should follow the [Dart style
guide](https://dart.dev/guides/language/effective-dart) and use `dart
format`.
- Java and Kotlin contributions should strive to follow Java and Kotlin
best practices
([discussion](#8098)).
</details>

Author: pq

flutter-idea/src/io/flutter/pub/PubRootCache.java

@@ -7,7 +7,6 @@
 
 import com.intellij.openapi.module.Module;
 import com.intellij.openapi.project.Project;
-import com.intellij.openapi.roots.ModuleRootManager;
 import com.intellij.openapi.vfs.VirtualFile;
 import com.intellij.psi.PsiFile;
 import io.flutter.utils.OpenApiUtils;

resources/META-INF/studio-contribs.xml

@@ -14,21 +14,22 @@
     <postStartupActivity implementation="io.flutter.FlutterStudioStartupActivity"/>
     <projectOpenProcessor implementation="io.flutter.editor.FlutterStudioProjectOpenProcessor" order="after flutter"/>
     <library.type implementation="io.flutter.android.AndroidModuleLibraryType"/>
-    <projectService serviceInterface="io.flutter.android.AndroidModuleLibraryManager"
-                    serviceImplementation="io.flutter.android.AndroidModuleLibraryManager"/>
+    <projectService serviceImplementation="io.flutter.android.AndroidModuleLibraryManager"/>
 
   </extensions>
 
   <actions>
 
     <!-- Define the 'New Flutter Project' menu item -->
+    <!--suppress PluginXmlI18n -->
     <action id="flutter.NewProject" class="io.flutter.actions.FlutterNewProjectAction"
             text="New Flutter Project..."
             description="Create a new Flutter project">
       <add-to-group group-id="JavaNewProjectOrModuleGroup" anchor="after" relative-to-action="NewProject"/>
     </action>
 
     <!-- The icon isn't being used here, but it is set by the action -->
+    <!--suppress PluginXmlI18n -->
     <action id="flutter.NewProject.welcome" class="io.flutter.actions.FlutterNewProjectAction"
             text="Create New Flutter Project"
             icon="FlutterIcons.Flutter"

resources/META-INF/studio-contribs_template.xml

@@ -12,21 +12,22 @@
     <postStartupActivity implementation="io.flutter.FlutterStudioStartupActivity"/>
     <projectOpenProcessor implementation="io.flutter.editor.FlutterStudioProjectOpenProcessor" order="after flutter"/>
     <library.type implementation="io.flutter.android.AndroidModuleLibraryType"/>
-    <projectService serviceInterface="io.flutter.android.AndroidModuleLibraryManager"
-                    serviceImplementation="io.flutter.android.AndroidModuleLibraryManager"/>
+    <projectService serviceImplementation="io.flutter.android.AndroidModuleLibraryManager"/>
 
   </extensions>
 
   <actions>
 
     <!-- Define the 'New Flutter Project' menu item -->
+    <!--suppress PluginXmlI18n -->
     <action id="flutter.NewProject" class="io.flutter.actions.FlutterNewProjectAction"
             text="New Flutter Project..."
             description="Create a new Flutter project">
       <add-to-group group-id="JavaNewProjectOrModuleGroup" anchor="after" relative-to-action="NewProject"/>
     </action>
 
     <!-- The icon isn't being used here, but it is set by the action -->
+    <!--suppress PluginXmlI18n -->
     <action id="flutter.NewProject.welcome" class="io.flutter.actions.FlutterNewProjectAction"
             text="Create New Flutter Project"
             icon="FlutterIcons.Flutter"