chore(migration): Do not touch release-please-manifest.json (#11113)

* fix(migration): Do not touch release-please-manifest.json

OwlBot automatically updates it.

* (fix) Do delete the copied-over manifest

---------

Co-authored-by: Anthonios Partheniou <partheniou@google.com>

scripts/split_repo_migration/split-repo-post-process.common-files.sh

@@ -160,20 +160,16 @@ jq ${RPC_SORT_KEYS} --argjson newObject "${RPC_NEW_OBJECT}" ". * {\"packages\":
 $RM ${RPC_SPLIT_PATH}
 ## END release-please config migration
 
-## START release-please manifest migration ########################################
+## START release-please manifest deletion ######################################
 # variable prefix: RPM_*
-RPM_MONO_PATH=".release-please-manifest.json"
-echo "Migrating: ${RPM_MONO_PATH}"
-
-# enable this if we want sorted keys. Keep it disabled to append new entries at
-# the end (useful for debugging):
-RPM_SORT_KEYS="${SORT_JSON_KEYS}"
-
+# We no longer need to add the package to the central file, since OwlBot does
+# that for us. However, we still need to delete the per-package manifest copied
+# over from the split repo.
 RPM_SPLIT_PATH="${PATH_PACKAGE}/.release-please-manifest.json"
-RPM_VERSION="$(jq '."."' "${RPM_SPLIT_PATH}")"
-jq ${RPM_SORT_KEYS}  ". * {\"${MONOREPO_PATH_PACKAGE}\": ${RPM_VERSION}}" ${RPM_MONO_PATH} | sponge ${RPM_MONO_PATH}
+echo "Deleting: ${RPM_SPLIT_PATH}"
+
 $RM ${RPM_SPLIT_PATH}
-## END release-please manifest migration
+## END release-please manifest deletion
 
 
 ## START .repo-metadata.json migration ########################################