Bump bundler to 4.0.12 #1889

Job	Run time
benchmark-graph	46s
benchmark-ractor (head)	6m 40s
test (head)	51s
benchmark-run-once	1m 37s
test (ruby)	46s
benchmark-ractor-only (head)	39s
benchmark-default (truffleruby, --excludes=knucleotide,lobsters,ruby-lsp,shipit)	13m 10s
test (truffleruby)	2m 1s
benchmark-default (head)	12m 23s
benchmark-default (ruby)	11m 19s
all-tests	2s
	50m 14s

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