Update v5.0.x PRTE submodule to OMPI-specific fork

Move the 3rd-party/prrte Git submodule to point to the
https://github.com/open-mpi/prrte repo, and update the specific git
hash to point to the tip of the v3.0-ompi-v5.0.x branch.

This branch points to a few commits beyond the upstream PRTE v3.0.10
tag to include some bug fixes that came in after the v3.0.10 release.
The additional commit in the Open MPI fork simply changes the version
number in the 3rd-party/prte tree (and adds a few docs) to make it
clear that this is an Open MPI-specific version of PRTE, and is not
the same as any upstream / community PRTE release.

Signed-off-by: Jeff Squyres <[email protected]>

Author: jsquyres

.gitmodules

@@ -1,6 +1,6 @@
 [submodule "prrte"]
 	path = 3rd-party/prrte
-	url = ../../openpmix/prrte
+	url = ../../open-mpi/prrte
 	branch = v3.0
 [submodule "openpmix"]
 	path = 3rd-party/openpmix