Fix the two sided test on IBMA Fishers and Stouffers estimators #1187

Job	Run time
Determine if CI should be skipped	5s
Unit tests with minimum dependency versions (ubuntu-latest, 3.8)	1h 0m 48s
Unit tests (ubuntu-latest, 3.8)	42m 52s
Corrector performance tests (ubuntu-latest, 3.8)	31m 6s
Unit tests (ubuntu-latest, 3.9)	41m 47s
CBMR ImportError tests (ubuntu-latest, 3.8)	59s
Estimator performance tests (ubuntu-latest, 3.8)	7m 26s
Unit tests (ubuntu-latest, 3.10)	41m 58s
Smoke performance tests (ubuntu-latest, 3.8)	21m 18s
Unit tests (ubuntu-latest, 3.11)	41m 6s
Unit tests (ubuntu-latest, 3.12)	45m 27s
Unit tests (macos-latest, 3.8)	46m 51s
Unit tests (macos-latest, 3.9)	25m 33s
Unit tests (macos-latest, 3.10)	23m 24s
Unit tests (macos-latest, 3.11)	22m 8s
Unit tests (macos-latest, 3.12)	24m 10s
Upload coverage	9s
	7h 57m 7s

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