Point the pipeline config to release branch for v0.25

Release v0.25.x branch has been created on pipeline side to add
documentation updates. Switch the config to the branch so that
we pull in any doc updates.
Signed-off-by: NAndrea Frittoli <andrea.frittoli@gmail.com>

sync/config/pipelines.yaml

@@ -74,7 +74,7 @@ tags:
       exclude:
       - api-spec.md
       - tutorial.md
-- name: v0.25.0
+- name: release-v0.25.x
   # The name to display on tekton.dev.
   # sync.py will use this value in the version switcher and other places.
   displayName: v0.25.0