RSpec: `aggregate_failures` tags are misspelled

Summary

If a typo of aggregate_failures is added to a spec, it currently fails silently.

This should raise an error instead.

More context

Relates to a community contribution MR. Looks like there are 8 references to aggregate_failure in the codebase, which is a no-op. There are also a few aggregated_failures and aggregated_errors

List

$ rg -I  -o -r '$2' "\b(it|context|describe).*, :\b(aggreg\w+_\w+)" spec ee/spec | sort | uniq -c | sort -gr

   2693 aggregate_failures # valid
     22 aggregate_errors
     11 aggregate_failure
      7 aggregated_failures
      2 aggregate_results
      2 aggregated_errors
      1 aggregates_failures
      1 aggregate_failues