Remove failing spec from memory_killer_spec.rb

This spec was redundant to another spec and caused failures in CI
because `rss_within_range?` was returning `nil`, which caused
`restart_sidekiq` to run and issue signals to kill processes.

Closes https://gitlab.com/gitlab-org/gitlab/issues/32342

spec/lib/gitlab/sidekiq_daemon/memory_killer_spec.rb

@@ -75,12 +75,6 @@ describe Gitlab::SidekiqDaemon::MemoryKiller do
       end
     end
 
-    it 'invoke rss_within_range? twice' do
-      expect(memory_killer).to receive(:rss_within_range?).twice
-
-      subject
-    end
-
     it 'not invoke restart_sidekiq when rss in range' do
       expect(memory_killer).to receive(:rss_within_range?).twice.and_return(true)