[CQ] remove (dead) FlutterStudioInitializer

[pq]

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 #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

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[pq]

Thanks!