[CQ] remove stale FlutterAppManager (#8165)

This service is unused.

Discovered when migrating parent disposables in pursuit of
#8107.

---

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portions to this PR.

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Author: pq

flutter-idea/src/io/flutter/run/FlutterAppManager.java

@@ -446,8 +446,6 @@
 
     <projectService serviceImplementation="io.flutter.run.FlutterReloadManager" overrides="false"/>
     <projectService serviceImplementation="io.flutter.editor.FlutterSaveActionsManager" overrides="false"/>
-    <projectService serviceImplementation="io.flutter.run.FlutterAppManager" overrides="false"/>
-
     <projectService serviceImplementation="io.flutter.editor.ActiveEditorsOutlineService" overrides="false"/>
 
     <iconProvider implementation="io.flutter.project.FlutterIconProvider" order="first"/>

resources/META-INF/plugin.xml

@@ -348,8 +348,6 @@
 
     <projectService serviceImplementation="io.flutter.run.FlutterReloadManager" overrides="false"/>
     <projectService serviceImplementation="io.flutter.editor.FlutterSaveActionsManager" overrides="false"/>
-    <projectService serviceImplementation="io.flutter.run.FlutterAppManager" overrides="false"/>
-
     <projectService serviceImplementation="io.flutter.editor.ActiveEditorsOutlineService" overrides="false"/>
 
     <iconProvider implementation="io.flutter.project.FlutterIconProvider" order="first"/>