Minor updates to covariance.rst file #13

Job	Run time
linux/3.9/bare-env	2s
win/3.11	2s
linux/3.13	1s
osx/3.12	3s
linux/3.10/mpi	1s
win/3.9/pip	3s
linux/3.11/conda	1s
lint/style-and-typos	2s
linux/3.12/cython	2s
process-coverage-${{ matrix.TARGET }}	1s
	18s

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