Don't set the SplashScreenDrawable for new projects

[jiahaog]

This is obsolete after #85292 was fixed. The preDraw listener returns false, keeping the initial android:windowBackground on screen until Flutter shows the first frame.

flutter/packages/flutter_tools/templates/app_shared/android.tmpl/app/src/main/res/values/styles.xml

Lines 5 to 7 in 76d5e62

	<!-- Show a splash screen on the activity. Automatically removed when
	Flutter draws its first frame -->
	<item name="android:windowBackground">@drawable/launch_background</item>

Related issue: #86955

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read and followed the Flutter Style Guide, including Features we expect every widget to implement.
• I signed the CLA.
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making or feature I am adding, or Hixie said the PR is test-exempt.
• All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel on Discord.

[blasten]

Nice!