ci: Use shallow submodules

.gitmodules

@@ -1,7 +1,9 @@
 [submodule "deps/mdnsd"]
 	path = deps/mdnsd
 	url = https://github.com/Pro/mdnsd.git
+	shallow = true
 [submodule "deps/ua-nodeset"]
 	path = deps/ua-nodeset
 	url = https://github.com/OPCFoundation/UA-Nodeset
 	branch = v1.04
+	shallow = true