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>
diff --git a/external_full.xml b/external_full.xml
index 4b1733e..96838b3 100644
--- a/external_full.xml
+++ b/external_full.xml
@@ -105,15 +105,12 @@
   <project path="src/third_party/toolbox"
            name="third_party/toolbox"
            revision="refs/heads/main" />
-  <project path="src/third_party/kernel/v5.4"
-           name="third_party/kernel"
-           revision="refs/heads/cos-5.4" />
-  <project path="src/third_party/kernel/v5.10"
-           name="third_party/kernel"
-           revision="refs/heads/cos-5.10" />
   <project path="src/third_party/kernel/v5.15"
            name="third_party/kernel"
            revision="refs/heads/cos-5.15" />
+  <project path="src/third_party/kernel/v6.1"
+           name="third_party/kernel"
+           revision="refs/heads/cos-6.1" />
 
   <repo-hooks enabled-list="pre-upload"
            in-project="cos/repohooks" />