turn off submodule updating for all testing submodules

Author: bcmyers

.gitmodules

@@ -1,9 +1,11 @@
 [submodule "parquet-testing"]
 	path = parquet-testing
 	url = https://github.com/apache/parquet-testing.git
+	update = none
 [submodule "testing"]
 	path = testing
 	url = https://github.com/apache/arrow-testing
+	update = none
 [submodule "datafusion-testing"]
 	path = datafusion-testing
 	url = https://github.com/apache/datafusion-testing.git