mon/OSDMonitor: Remove check for FLAG_NOPGCHANGE for crimson pools

mon/OSDMonitor: Remove check for FLAG_NOPGCHANGE for crimson pools

With PG Splitting introduced, we can remove the check that previously stopped changes in pg_num for crimson pools.

Note: `nopgchange` is set to true by default with Crimson pools,
      for pg_num changes to actually take place we should also set `nopgchange` to false.
      Currently, this is used for (PG splitting) testing only. Once PG merging is in place as well,
      we could revert `nopgchange` to be false by default in Crimson.

Signed-off-by: Aishwarya Mathuria <amathuri@redhat.com>