pgsql: ci: Upgrade macOS version from 12 to 13.

ci: Upgrade macOS version from 12 to 13. Back-patch to 15, where in-tree CI began. Author: Justin Pryzby Discussion: https://postgr.es/m/1441145.1675300332%40sss.pgh.pa.us Branch -- REL_15_STABLE Details --- https://git.postgresql.org/pg/commitdiff/83c7e2f2a2f541b5adc11c9d2826eeaf2a223

pgsql: ci: Upgrade macOS version from 12 to 13.

ci: Upgrade macOS version from 12 to 13. Back-patch to 15, where in-tree CI began. Author: Justin Pryzby Discussion: https://postgr.es/m/1441145.1675300332%40sss.pgh.pa.us Branch -- master Details --- https://git.postgresql.org/pg/commitdiff/2e9f120b657e540b36843dbb075dab196e79fbfd Mo