bump(android): kotlin language version from 1.4 to 1.6

[buenaflor]

📜 Description

Fixes usage with Kotlin 2.1.0 which requires at least a language version of 1.6

📝 Checklist

• I reviewed submitted code
• I added tests to verify changes
• No new PII added or SDK only sends newly added PII if sendDefaultPii is enabled
• I updated the docs if needed
• All tests passing
• No breaking changes

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.83%. Comparing base (05933ac) to head (80e955d).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2456      +/-   ##
==========================================
+ Coverage   86.84%   91.83%   +4.98%     
==========================================
  Files         260       84     -176     
  Lines        9239     2904    -6335     
==========================================
- Hits         8024     2667    -5357     
+ Misses       1215      237     -978     

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