Downgrade Android gradle plugin

[TimvdLippe]

The newer version is only compatible with new versions of
IntelliJ/Android Studio. To ensure that older versions of IntelliJ can
still open this project, we should downgrade our version for now.

This Gradle plugin version supports IntelliJ 2020.3 and newer.

Fixes #2378

[codecov-commenter]

Codecov Report

Merging #2380 (be268a2) into main (f8da4ce) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##               main    #2380   +/-   ##
=========================================
  Coverage     84.77%   84.77%           
  Complexity     2792     2792           
=========================================
  Files           328      328           
  Lines          8490     8490           
  Branches       1026     1026           
=========================================
  Hits           7197     7197           
  Misses         1015     1015           
  Partials        278      278           

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