[release] Add 2.10.2 to entry to the changelog
[release] Add 2.10.2 to entry to the changelog

TBR=a821cddceae7dc400f272e3cb1a72f400f9fed6d@google.com

Change-Id: Iaa48d09b60f160b44a7936c630f7970c3531c837
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/167341
Reviewed-by: Alexander Thomas <29642742b6693024c89de8232f2e2542cf7eedf7@google.com>
Reviewed-by: William Hesse <a821cddceae7dc400f272e3cb1a72f400f9fed6d@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk