Update third_party/kernel to point to main branches instead of release.

BUG=None
TEST=repo init and sync
RELEASE_NOTE=None

Change-Id: I8d21a6248ff1c80c3deca250b2bc09b08c14860a
Reviewed-on: https://cos-review.googlesource.com/c/cos/manifest/+/35647
Reviewed-by: Arnav Kansal <rnv@google.com>
Tested-by: Meena Shanmugam <meenashanmugam@google.com>
diff --git a/external_full.xml b/external_full.xml
index 1ad3d45..00dffe8 100644
--- a/external_full.xml
+++ b/external_full.xml
@@ -112,13 +112,13 @@
            revision="refs/heads/release-R101" />
   <project path="src/third_party/kernel/v5.4"
            name="third_party/kernel"
-           revision="refs/heads/release-R101-cos-5.4" />
+           revision="refs/heads/main-R101-cos-5.4" />
   <project path="src/third_party/kernel/v5.10"
            name="third_party/kernel"
-           revision="refs/heads/release-R101-cos-5.10" />
+           revision="refs/heads/main-R101-cos-5.10" />
   <project path="src/third_party/kernel/v5.15"
            name="third_party/kernel"
-           revision="refs/heads/release-R101-cos-5.15" />
+           revision="refs/heads/main-R101-cos-5.15" />
 
   <repo-hooks enabled-list="pre-upload"
            in-project="cos/repohooks" />