Remove the max api microversion assertion

max api microversion assertion should be removed here, because
microversion change patches for manila need to trigger this
plugging, but this plugging still test old version microversion
tests, this will cause manila-tempest-minimal-dsvm-dummy job
never passed.

Change-Id: Ib691a0925e29f90bf6d5b0a22fa8b03c9fe176cf
1 file changed