Use targetSdkVersion 34 for Android platform AndroidManifest.xml

[gmackall]

#47609 just landed, changing the engine to use the latest android sdk.

See the last time this was done #47683

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 and the C++, Objective-C, Java style guides.
• I listed at least one issue that this PR fixes in the description above.
• I added new tests to check the change I am making or feature I am adding, or the PR is test-exempt. See testing the engine for instructions on writing and running engine tests.
• I updated/added relevant documentation (doc comments with ///).
• I signed the CLA.
• All existing and new tests are passing.

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

[gmackall]

Closing, as the original PR to bump the engine to api 34 was reverted and needs to include this directly in the reland (which is here #47839)