Don't use nightly libtpu for torch_xla release

Author: bhavya01

setup.py

@@ -110,7 +110,7 @@
 # 4. After the local build succeeds, create a PR and wait for the CI result. Fix
 #    CI errors as needed until all required checks pass.
 
-USE_NIGHTLY = True  # Whether to use nightly or stable libtpu and JAX.
+USE_NIGHTLY = False  # Whether to use nightly or stable libtpu and JAX.
 
 _libtpu_version = '0.0.21'
 _libtpu_date = '20250813'