docs/rocm: fix syntax of osu_latency benchmark

fix the syntax for running the osu_latency benchmark for device memory.
`-d rocm` is only required for the collective osu benchmark tests, not
for the p2p ones.

Signed-off-by: Edgar Gabriel <Edgar.Gabriel@amd.com>
(cherry picked from commit 1064202)

docs/tuning-apps/networking/rocm.rst

@@ -79,7 +79,7 @@ using Open MPI and UCX ROCm support is something like this:
 .. code-block::
 
    shell$ mpirun -n 2 --mca pml ucx \
-           ./osu_latency -d rocm D D
+           ./osu_latency D D
 
 Note: some additional configure flags are required to compile the OSU
 benchmark to support ROCm buffers. Please refer to the `UCX ROCm