nightly: Rename OMPI master to main

Signed-off-by: Brian Barrett <bbarrett@amazon.com>

Author: bwbarrett

nightly-tarball/openmpi-nightly-tarball

@@ -29,7 +29,7 @@ config_data = { 'project_name' : 'Open MPI',
                                'configure_args' : '--enable-debug --enable-mpi-fortran --enable-mpi-java --enable-oshmem --enable-oshmem-fortran --with-usnic --with-libfabric=/mnt/data/local-installs --with-ucx=/mnt/data/local-installs',
                                'make_args' : '-j 2',
                                'email' : 'jsquyres@cisco.com' },
-                'branches' : { 'master' : { 'output_location' : 'master/',
+                'branches' : { 'main' : { 'output_location' : 'main/',
                                             'coverity' : True,
                                             'max_count' : 7 },
                                'v5.0.x' : { 'output_location' : 'v5.0.x/',