cmake: remove cython 0.29's subinterpreter check during install
Commit
3bde34af8a removed cython 0.29's subinterpreter check when
building the various python modules during `make`, but unforunately
they're *rebuilt* during `make install`, with the rebuild overwriting
the original build. The original fix was of course missing from the
install stage...
Fixes: https://tracker.ceph.com/issues/38788
Signed-off-by: Tim Serong <tserong@suse.com>
(cherry picked from commit
108462e3fb0e814c98ab32f02b79cf3ea1247692)