Updated the android gradle version

[pmathew92]

• All new/changed/fixed functionality is covered by tests - N/A
• I have added documentation for all new/changed functionality - N/A

📋 Changes

This PR updates the gradle version to 8.6

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.31%. Comparing base (253209a) to head (331490f).
Report is 58 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #490      +/-   ##
============================================
+ Coverage     96.08%   96.31%   +0.22%     
============================================
  Files            97       98       +1     
  Lines          1611     1602       -9     
  Branches        331      348      +17     
============================================
- Hits           1548     1543       -5     
- Misses           49       50       +1     
+ Partials         14        9       -5     

Flag	Coverage Δ
auth0_flutter	100.00% <ø> (ø)
auth0_flutter_android	97.28% <ø> (+0.72%)	⬆️
auth0_flutter_ios	99.70% <ø> (-0.14%)	⬇️
auth0_flutter_platform_interface	87.06% <ø> (+0.03%)	⬆️

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