Remove redundant method overwrite in spec_helper

[Earlopain]

These implementations are now identical since at least tmm1/test-queue#124

/home/user/Documents/rubocop/spec/spec_helper.rb:73: warning: method redefined; discarding old failure_count
/home/user/rbenv/versions/3.3.1/lib/ruby/gems/3.3.0/gems/test-queue-0.11.1/lib/test_queue/runner/rspec_ext.rb:4: warning: previous definition of failure_count was here

https://github.com/tmm1/test-queue/blob/e1674e1ec49e76cbbf68d83d2bc03aef83ce4e68/lib/test_queue/runner/rspec_ext.rb#L5

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