[CQ] remove (dead) FlutterStudioInitializer (flutter#8212)

`FlutterStudioInitializer` exists to perform a check at startup to
ensure AS is current enough for... something...
I can't recall the motivation for this extra check (despite having
reviewed it in flutter#1346 😬)
but it was **8 years ago**!

Needless to say, removing it is surely safe:

1. the `com.intellij.androidStudioInitializer` extension point seems to
have gone away, and even if it hadn't,
2. we're surely past the window where there are any version out there
that are too early for the version check




---

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

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  <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
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</details>

Author: pq

flutter-studio/src/io/flutter/FlutterStudioInitializer.java

@@ -10,7 +10,6 @@
 
   <extensions defaultExtensionNs="com.intellij">
     <externalSystemTaskNotificationListener implementation="io.flutter.utils.FlutterExternalSystemTaskNotificationListener"/>
-    <androidStudioInitializer implementation="io.flutter.FlutterStudioInitializer"/>
     <postStartupActivity implementation="io.flutter.FlutterStudioStartupActivity"/>
     <projectOpenProcessor implementation="io.flutter.editor.FlutterStudioProjectOpenProcessor" order="after flutter"/>
     <library.type implementation="io.flutter.android.AndroidModuleLibraryType"/>

resources/META-INF/studio-contribs.xml

@@ -8,7 +8,6 @@
 
   <extensions defaultExtensionNs="com.intellij">
     <externalSystemTaskNotificationListener implementation="io.flutter.utils.FlutterExternalSystemTaskNotificationListener"/>
-    <androidStudioInitializer implementation="io.flutter.FlutterStudioInitializer"/>
     <postStartupActivity implementation="io.flutter.FlutterStudioStartupActivity"/>
     <projectOpenProcessor implementation="io.flutter.editor.FlutterStudioProjectOpenProcessor" order="after flutter"/>
     <library.type implementation="io.flutter.android.AndroidModuleLibraryType"/>