API level 30 upgrade: AOSP/Launcher3

The AndroidManifest.xml and build.gradle file of the AOSP
Launcher app has been upgraded so that its targetSdkVersion
is 30. This change has been made on git_master so that
we can avoid presubmit conflicts when making this change
on the aosp-master branch.

Change-Id: Ie476f8cbe56bf51218b15b8361a22fec2dc845e6