chore: no more impeller explicit opt-out

[monsieurtanuki]

What

• Each time we started the app on the emulator, we got that annoying message

I/flutter (19545): [IMPORTANT:flutter/shell/common/shell.cc(528)] [Action Required]: Impeller
opt-out deprecated.
I/flutter (19545):     The application opted out of Impeller by either using the
I/flutter (19545):     `--no-enable-impeller` flag or the
I/flutter (19545):     `io.flutter.embedding.android.EnableImpeller` `AndroidManifest.xml` entry.
I/flutter (19545):     These options are going to go away in an upcoming Flutter release. Remove
I/flutter (19545):     the explicit opt-out. If you need to opt-out, please report a bug describing
I/flutter (19545):     the issue.
I/flutter (19545):
I/flutter (19545):     https://github.com/flutter/flutter/issues/new?template=02_bug.yml
I/flutter (19545):

• this PR removes that Impeller opt-out.
• fun fact: the morons at flutter/dart/android studio had the terrific idea to change the display format of xml (xml!). As a consequence, it may not be obvious but I just removed the Impeller opt-out option.

Part of

• chore: Disable Impeller for Android devices #6375

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 8.99%. Comparing base (4d9c7fc) to head (64ed217).
⚠️ Report is 1388 commits behind head on develop.

Additional details and impacted files

@@            Coverage Diff             @@
##           develop   #7502      +/-   ##
==========================================
- Coverage     9.54%   8.99%   -0.56%     
==========================================
  Files          325     638     +313     
  Lines        16411   37282   +20871     
==========================================
+ Hits          1567    3353    +1786     
- Misses       14844   33929   +19085     

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