ci: windows: Use CIRRUS_ESCAPING_PROCESSES, revert 770011e3f39.

ci: windows: Use CIRRUS_ESCAPING_PROCESSES, revert 770011e3f39.

cirrus-ci now defaults to killing processes still running at the end of a
script. Unfortunately we start postgres in the background, which seems
nontrivial to fix. Previously we worked around that in 770011e3f39 by using an
older agent version, but now that CIRRUS_ESCAPING_PROCESSES we should use that.

This reverts commit 770011e3f39f21f2095d3a044b72460c4efac345 "ci: windows:
Work around cirrus-ci bug causing test failures.

Discussion: https://postgr.es/m/CA+hUKGKx7k14n2nAALSvv6M_AB6oHasNBA65X6Dvo8hwfi9y0A@mail.gmail.com