Update third_party/checkstyle to 7.6.1

This CL updates third_party/checkstyle to 7.6.1 so checkstyle would
work with Java 8 lambda features.

BUG=703238

Review-Url: https://codereview.chromium.org/2799303003
Cr-Original-Commit-Position: refs/heads/master@{#462968}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: dbce02f63421f7d446d6ef317b456f6ae911f63b
1 file changed