Bump urllib3 from 2.5.0 to 2.6.3 in /images/ci-prune-buildcache #1053

Job	Run time
check-modified-dirs	5s
build (./images/ci-prune-buildcache, ghcr.io/spack/ci-prune-buildcache:0.0.5)	3m 8s
	3m 13s

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