Fix the correlation matrix computation in Stouffers and Reports #1178

Job	Run time
Determine if CI should be skipped	4s
CBMR ImportError tests (ubuntu-latest, 3.8)	56s
Unit tests with minimum dependency versions (ubuntu-latest, 3.8)	42m 48s
Unit tests (ubuntu-latest, 3.8)	43m 48s
Corrector performance tests (ubuntu-latest, 3.8)	31m 9s
Estimator performance tests (ubuntu-latest, 3.8)	6m 56s
Unit tests (ubuntu-latest, 3.9)	40m 37s
Smoke performance tests (ubuntu-latest, 3.8)	20m 37s
Unit tests (ubuntu-latest, 3.10)	43m 24s
Unit tests (ubuntu-latest, 3.11)	39m 42s
Unit tests (ubuntu-latest, 3.12)	42m 1s
Unit tests (macos-latest, 3.8)	46m 15s
Unit tests (macos-latest, 3.9)	23m 41s
Unit tests (macos-latest, 3.10)	23m 22s
Unit tests (macos-latest, 3.11)	25m 38s
Unit tests (macos-latest, 3.12)	25m 22s
Upload coverage	0s
	7h 36m 20s

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