[many] More v1 embedding deletion that was missed in flutter/packages#6494 (#6923)

There were some additional v1 Android embedding references missed by flutter/packages#6494.

This PR aims to remove those missed references.

I built the android example app of each plugin affected here on the [deletion branch](flutter-team-archive/engine#52022) to be completely sure:

Final testing, I tested that the `all_packages` app builds on the v1 embedding deletion branch: 
```
$ ./.ci/scripts/create_all_packages_app.sh && cd all_packages
...
$ flutter build apk --debug --local-engine-src-path=/Users/mackall/development/engine/src --local-engine=android_debug_arm64 --local-engine-host=host_debug

Running Gradle task 'assembleDebug'...                              4.8s
� Built build/app/outputs/flutter-apk/app-debug.apk
```

� 

Linux repo checks are failing 
```
The following packages had errors:
  packages/google_maps_flutter/google_maps_flutter:
    Missing CHANGELOG change
  packages/palette_generator:
    Missing CHANGELOG change
  packages/quick_actions/quick_actions:
    Missing CHANGELOG change
  packages/webview_flutter/webview_flutter:
    Missing CHANGELOG change
```
The only changes to these packages are `xml` changes to example apps which won't cause build failures even when the v1 embedding is deleted (they will just be unused). So I believe these changes should be version exempt.

Author: gmackall

google_maps_flutter/example/android/app/src/main/AndroidManifest.xml

@@ -16,9 +16,6 @@
             android:configChanges="orientation|keyboardHidden|keyboard|screenSize|locale|layoutDirection|fontScale"
             android:hardwareAccelerated="true"
             android:windowSoftInputMode="adjustResize">
-            <meta-data
-                android:name="io.flutter.app.android.SplashScreenUntilFirstFrame"
-                android:value="true" />
             <intent-filter>
                 <action android:name="android.intent.action.MAIN"/>
                 <category android:name="android.intent.category.LAUNCHER"/>

google_maps_flutter_android/example/android/app/src/main/AndroidManifest.xml

@@ -17,9 +17,6 @@
             android:configChanges="orientation|keyboardHidden|keyboard|screenSize|locale|layoutDirection|fontScale"
             android:hardwareAccelerated="true"
             android:windowSoftInputMode="adjustResize">
-            <meta-data
-                android:name="io.flutter.app.android.SplashScreenUntilFirstFrame"
-                android:value="true" />
             <intent-filter>
                 <action android:name="android.intent.action.MAIN"/>
                 <category android:name="android.intent.category.LAUNCHER"/>