fix docs code example

Change-Id: I7b262725e6eedaeef9ebc0e956cae515b68ed9cd

diff --git a/doc/build/changelog/migration_21.rst b/doc/build/changelog/migration_21.rst
index d6ca0198bff0e4fc009d9e399289eed8a32c39f5..2ef92b7db7decff21a4bfc8bb83cc9025a4e0241 100644 (file)
--- a/doc/build/changelog/migration_21.rst
+++ b/doc/build/changelog/migration_21.rst
@@ -1071,7 +1071,9 @@ the new SQL syntax. The index definitions that used the arrow operator
 syntax (``h -> 'key'``) will not match the new subscript syntax
 (``h['key']``), which may cause index scans to not be used.
 
-To update an existing index::
+To update an existing index:
+
+.. sourcecode:: sql
 
     -- Drop the old index
     DROP INDEX IF EXISTS idx_hstore_key;