Point to the master branches.

Issue-Ref: 3620
Signed-off-by: Alexander Diewald <diewald@fortiss.org>

.gitmodules

 [submodule "releng/org.fortiss.af3.target"]
 	path = releng/org.fortiss.af3.target
 	url = https://git.fortiss.org/af3/target-definition.git
+	branch = master
 [submodule "bundles/af3"]
 	path = bundles/af3
 	url = https://git.fortiss.org/af3/af3.git
-	branch = 3620
+	branch = master
 	fetchRecurseSubmodules = true
 [submodule "bundles/kernel"]
 	path = bundles/kernel
 	url = https://git.fortiss.org/af3/kernel.git
-	branch = 3620
+	branch = master
 	fetchRecurseSubmodules = true
 [submodule "tests/af3"]
 	path = tests/af3
 	url = https://git.fortiss.org/af3/af3-tests.git
+	branch = master
 [submodule "features/af3"]
 	path = features/af3
 	url = https://git.fortiss.org/af3/af3-features.git