Revert "Use relative submodule URLs"

This reverts commit 5e48667f for now until
<https://gerrit-review.googlesource.com/#/c/36190/> "Expanded submodule
subscription support" is fixed, as it inadvertently caused gerrit to no longer
automatically create corresponding core commits whenever receiving submodule
commits (whether or not that is actually a good feature).

.gitmodules

 [submodule "binfilter"]
 	path = binfilter
-	url = ../binfilter
+	url = git://gerrit.libreoffice.org/binfilter
 	branch = .
 [submodule "dictionaries"]
 	path = dictionaries
-	url = ../dictionaries
+	url = git://gerrit.libreoffice.org/dictionaries
 	branch = .
 [submodule "helpcontent2"]
 	path = helpcontent2
-	url = ../help
+	url = git://gerrit.libreoffice.org/help
 	branch = .
 [submodule "translations"]
 	path = translations
-	url = ../translations
+	url = git://gerrit.libreoffice.org/translations
 	branch = .