pgsql: ci: macos: Reduce test concurrency

ci: macos: Reduce test concurrency

Test performance regresses noticably when using all cores. This is more
pronounced with meson than with autoconf, presumably because meson will
schedule the "full number" of tests more consistently. 8 seems to work
OK.

Discussion: /messages/by-id/20220927040208.l3shfcidovpzqxfh@awork3.anarazel.de
Backpatch: 15-, where CI was introduced

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/2d2f08310490d63c4cc097243ba63a1601316c17

Modified Files
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.cirrus.yml | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)