Update .gitmodule (#2)

* Adopt progsigma "Add prognostic cumulus closure description in saSAS NOAA-EMC#523"
https://github.com/NOAA-EMC/fv3atm/pull/523/files

	modified:   ../ccpp/data/CCPP_typedefs.F90
	modified:   ../ccpp/data/GFS_typedefs.F90
	modified:   ../ccpp/data/GFS_typedefs.meta
	modified:   ../ccpp/driver/GFS_restart.F90
	modified:   stochastic_physics_wrapper.F90

* modified:   .gitmodules

.gitmodules

@@ -8,8 +8,8 @@
   branch = main
 [submodule "ccpp/physics"]
   path = ccpp/physics
-  url = https://github.com/NCAR/ccpp-physics
-  branch = release/public-v6
+  url = https://github.com/DTC-phytne/ccpp-physics
+  branch = progsigma
 [submodule "upp"]
   path = upp
   url = https://github.com/NOAA-EMC/UPP