Specify absolute templates submodule path

This way people who want to contribute changes from forks don't experience a failing pipeline without forking the templates repo as well.

@jandt-desy Is this fine from your side. This is required to fix the pipeline in !504 (closed) for instance.

.gitmodules

@@ -12,4 +12,4 @@
 	url = https://github.com/jquery/jquery.git
 [submodule "submodules/templates"]
 	path = submodules/templates
-	url = ../templates.git
+	url = https://gitlab.hzdr.de/hifis/overall/templates.git