Merge pull request #18670 from stanley-cheung/remove-submodule

Fix third_party/protoc-gen-validate

.gitmodules

@@ -50,7 +50,7 @@
 	url = https://github.com/googleapis/googleapis.git
 [submodule "third_party/protoc-gen-validate"]
 	path = third_party/protoc-gen-validate
-	url = https://github.com/lyft/protoc-gen-validate.git
+	url = https://github.com/envoyproxy/protoc-gen-validate.git
 [submodule "third_party/upb"]
 	path = third_party/upb
 	url = https://github.com/google/upb.git