Add Android M requirement for two accessibility tests on Android

This CL updates two tests to require Android M to run.

The tests cannot complete on lollipop but will work on any platform
after and including M, so we add an annotation to require Android M
for each of the two tests.

AX-Relnotes: N/A
Bug: 1161533, 1162284
Change-Id: Ib56726674aad7e2fab8473a3d5f50b38d24f2564
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3025782
Reviewed-by: Mark Schillaci <mschillaci@google.com>
Reviewed-by: Abigail Klein <abigailbklein@google.com>
Commit-Queue: Mark Schillaci <mschillaci@google.com>
Cr-Commit-Position: refs/heads/master@{#901613}