Android: Remove obsolete JUnit3 SDK targets

And removes our local modifications to //third_party/junit

Bug: 40693265
Change-Id: I00b2625f9bbab9bfaf83c9a82c8541d68961b2ba
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5346656
Reviewed-by: Henrique Nakashima <hnakashima@chromium.org>
Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Owners-Override: Andrew Grieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1269637}
NOKEYCHECK=True
GitOrigin-RevId: e29e1902395edd716f1bb5faccbc5db389998dce