fix for PotatoCenter:compileFlutterBuildRelease FAILED error when building POSP (baked-release)

flutter fix

## fix for PotatoCenter:compileFlutterBuildRelease FAILED error when building POSP (baked-release)

# The error
```
> Task :PotatoCenter:compileFlutterBuildRelease FAILED
         *********************************************************
WARNING: This version of shared_preferences will break your Android build if it or its dependencies aren't compatible with AndroidX.
         See https://goo.gl/CP92wY for more information on the problem and how to fix it.
         This warning prints for all Android build failures. The real root cause of the error may be unrelated.
         *********************************************************
 ```
 # the cause 
 This error is cause  by  using a newer version of flutter

# how to fix it
apply this to your local manifest:
```
<remove-project path="external/flutter" name="flutter/flutter" remote="github" />
<project name="flutter/flutter" path="external/flutter" revision="v1.9.1-hotfixes" remote="github" />