tests: Remove test_change_invite_to_realm_policy from test_realm.py.
tests: Remove test_change_invite_to_realm_policy from test_realm.py.

This commit removes test_change_invite_to_realm_policy which is used
to test changing invite_to_realm_policy using 'PATCH /realm' endpoint
as we already do this in do_test_realm_update_api and invalid value
is also tested in test_invalid_integer_attribute_values.

kou/zulip,eeshangarg/zulip,andersk/zulip,andersk/zulip,hackerkid/zulip,hackerkid/zulip,kou/zulip,andersk/zulip,kou/zulip,rht/zulip,punchagan/zulip,hackerkid/zulip,punchagan/zulip,eeshangarg/zulip,eeshangarg/zulip,rht/zulip,rht/zulip,punchagan/zulip,eeshangarg/zulip,kou/zulip,zulip/zulip,eeshangarg/zulip,rht/zulip,punchagan/zulip,kou/zulip,andersk/zulip,kou/zulip,zulip/zulip,zulip/zulip,rht/zulip,zulip/zulip,hackerkid/zulip,rht/zulip,andersk/zulip,eeshangarg/zulip,rht/zulip,zulip/zulip,hackerkid/zulip,andersk/zulip,hackerkid/zulip,hackerkid/zulip,zulip/zulip,punchagan/zulip,eeshangarg/zulip,kou/zulip,punchagan/zulip,punchagan/zulip,zulip/zulip,andersk/zulip