Update docs to remove oppia-android-dev@ list (which is deprecated) and mentions of individual mentors (we now handle queries on GitHub Discussions).

[seanlip]

Explanation

Removes the deprecated oppia-android-dev@ list and directs contributors to GitHub Discussions. Also cleans up mentions of individual mentor assignment since we now use Discussions for handling queries.

Essential Checklist

• The PR title and explanation each start with "Fix #bugnum: " (If this PR fixes part of an issue, prefix the title with "Fix part of #bugnum: ...".) -- N/A
• Any changes to scripts/assets files have their rationale included in the PR explanation.
• The PR follows the style guide.
• The PR does not contain any unnecessary code changes from Android Studio (reference).
• The PR is made from a branch that's not called "develop" and is up-to-date with "develop".
• The PR is assigned to the appropriate reviewers (reference).

[github-actions]

Coverage Report

Results

Number of files assessed: 2
Overall Coverage: 98.00%
Coverage Analysis: PASS ✅

Passing coverage

Files with passing code coverage

File	Coverage	Lines Hit	Status	Min Required
CoroutineExecutorService.kt testing/src/main/java/org/oppia/android/testing/threading/CoroutineExecutorService.kt	98.00%	98 / 100	✅	70%

Exempted coverage

Files exempted from coverage

File	Exemption Reason
TestCoroutineDispatchers.kt testing/src/main/java/org/oppia/android/testing/threading/TestCoroutineDispatchers.kt	This file is exempted from having a test file; skipping coverage check.

Refer test_file_exemptions.textproto for the comprehensive list of file exemptions and their required coverage percentages.

To learn more, visit the Oppia Android Code Coverage wiki page