[ServerGlobalCallbacks] Experiment defaults true

Author: yashykt

src/core/lib/experiments/experiments.cc

@@ -243,7 +243,7 @@
     ]
 - name: server_global_callbacks_ownership
   description: If set, server global callbacks ownership is fixed to not be owned by gRPC.
-  expiry: 2025/06/30
+  expiry: 2025/09/30
   owner: [email protected]
   test_tags: []
 - name: shard_global_connection_pool

src/core/lib/experiments/experiments.h

@@ -83,7 +83,7 @@
 - name: schedule_cancellation_over_write
   default: false
 - name: server_global_callbacks_ownership
-  default: false
+  default: true
 - name: shard_global_connection_pool
   default: true
 - name: sleep_promise_exec_ctx_removal