.gitmodules: update smmap url

RandyMcMillan · Byron · commit 2ce0e3175bcb · 2022-03-16T07:30:11.000+08:00
Github.com is currenly redirecting the smmap url: https://github.com/Byron/smmap.git to: https://github.com/gitpython-developers/smmap For correctness we update to the url directly
diff --git a/.gitmodules b/.gitmodules
@@ -1,3 +1,3 @@
 [submodule "smmap"]
 	path = gitdb/ext/smmap
-	url = https://github.com/Byron/smmap.git
+	url = https://github.com/gitpython-developers/smmap.git
