Changed remote for dates submodule (use https protocol instead of ssh, dynbot...

Changed remote for dates submodule (use https protocol instead of ssh, dynbot is not a known user for GitHub).

.gitmodules

@@ -15,5 +15,5 @@
 	url = https://github.com/DynareTeam/m-unit-tests.git
 [submodule "matlab/modules/dates"]
 	path = matlab/modules/dates
-	url = git@github.com:DynareTeam/dates.git
+	url = https://github.com/DynareTeam/dates.git
 	branch = old-oop-syntax