Add entry for 6.1 kernel in manifest. cleanup: removing entries for 5.4 and 5.10 BUG=b/266653416 TEST=repo sync --manifest-name=$HOME/cos/manifest/external_full.xml RELEASE_NOTE=None Change-Id: Ibb4e7f12d2f9291590168cf3cb15780e4dc98b85 Reviewed-on: https://cos-review.googlesource.com/c/cos/manifest/+/41451 Reviewed-by: Oleksandr Tymoshenko <ovt@google.com> Tested-by: Varsha Teratipally <teratipally@google.com>