Fix missing notifications in Messaging app

[FullStackFlamingo]

I noticed I wasn't getting any notifications from the default Messaging app, seems that the SDK version is set too high without Google adding the logic code for it.

I'm surprised no one else has noticed this, so feel free to ignore this PR if it you can't replicate it. I'm building AOSP locally based on your script (thanks for making it!). So it's possible I'm getting a different version of the Messaging app somehow.

Tested on my sargo. QQ1A.191205.011 , android-10.0.0_r16

The quick hacky fix that was implemented:
https://android.googlesource.com/platform/packages/apps/Messaging/+/8e71d1b707123e1b48b5529b1661d53762922400%5E!/

The logic they should have merged:
https://developer.android.com/training/notify-user/channels

[dan-v]

Thanks @FullStackFlamingo! I remember bumping into this issue initially and for some reason I had thought it was already fixed upstream (but apparently not). I don't use the default messaging app, so that's probably why I didn't see this. They also did a similar hack with alarm clock https://android.googlesource.com/platform/packages/apps/DeskClock/+/e6351b3b85b2f5d53d43e4797d3346ce22a5fa6f. Anyways, thanks a bunch!