Fix .gitmodules for pthreadpool

Author: mcr229

.gitmodules

@@ -27,7 +27,7 @@
 	url = https://github.com/pytorch/cpuinfo.git
 [submodule "backends/xnnpack/third-party/pthreadpool"]
 	path = backends/xnnpack/third-party/pthreadpool
-	url = https://github.com/Maratyszcza/pthreadpool.git
+	url = https://github.com/google/pthreadpool.git
 [submodule "extension/llm/tokenizers"]
 	path = extension/llm/tokenizers
 	url = https://github.com/pytorch-labs/tokenizers.git