Set supports_partitioned_indexes to false

This was false until we bumped our advertised PostgreSQL version in
v21.1. I set it back to false since it was causing a test failure.

Author: solongordon

lib/active_record/connection_adapters/cockroachdb_adapter.rb

@@ -173,6 +173,10 @@ def supports_string_to_array_coercion?
         @crdb_version >= 202
       end
 
+      def supports_partitioned_indexes?
+        false
+      end
+
       # This is hardcoded to 63 (as previously was in ActiveRecord 5.0) to aid in
       # migration from PostgreSQL to CockroachDB. In practice, this limitation
       # is arbitrary since CockroachDB supports index name lengths and table alias