Fix release notes in emails

To be cherry-picked for #2246.

--
Change-Id: I50bbd7dc00e4305f36d9a2a3a8841d6d9bcd2bd7
Reviewed-on: https://cr.bazel.build/8034
PiperOrigin-RevId: 142524920
MOS_MIGRATED_REVID=142524920

scripts/ci/build.sh

@@ -175,7 +175,7 @@ function generate_email() {
   local args=(
       "%release_name%" "${release_name}"
       "%rc%" "${rc}"
-      "%relnotes%" "# $(git_commit_msg)"
+      "%relnotes%" "# $(get_full_release_notes)"
   )
   if [ -n "${rc}" ]; then
     args+=(