Reverting changes to .gitmodule (I still get timed out if I'm not connected...

Reverting changes to .gitmodule (I still get timed out if I'm not connected via the ETH network for gitlab.math.ethz.ch

.gitmodules

 [submodule "Betl2"]
 	path = Betl2
-	url = git@gitlab.math.ethz.ch:NumPDE/Betl2.git
+	url = https://gitlab.math.ethz.ch/NumPDE/Betl2.git