tests: Remove redundant test_notify_settings test.
tests: Remove redundant test_notify_settings test.

We already test all the notification settinsg in
test_toggling_boolean_display_settings (which is
now renamed to test_toggling_boolean_user_settings)
as all settings are now moved to property_types and
we are merging other parts also to consider all the
settings under one category.

andersk/zulip,eeshangarg/zulip,zulip/zulip,rht/zulip,zulip/zulip,eeshangarg/zulip,rht/zulip,andersk/zulip,zulip/zulip,eeshangarg/zulip,eeshangarg/zulip,rht/zulip,kou/zulip,rht/zulip,zulip/zulip,andersk/zulip,eeshangarg/zulip,andersk/zulip,rht/zulip,zulip/zulip,eeshangarg/zulip,kou/zulip,andersk/zulip,kou/zulip,kou/zulip,kou/zulip,kou/zulip,rht/zulip,andersk/zulip,eeshangarg/zulip,zulip/zulip,kou/zulip,zulip/zulip,andersk/zulip,rht/zulip