dashboard/app: use machines with more memory for batch processing #16132

Job	Run time
build	3m 27s
dashboard	2m 11s
aux	5m 14s
arch (presubmit_arch_linux)	10m 25s
arch (presubmit_arch_darwin)	3m 55s
arch (presubmit_arch_openbsd)	3m 40s
race_dashboard	3m 10s
old	6m 51s
arch (presubmit_arch_freebsd)	6m 29s
arch (presubmit_arch_windows)	3m 31s
arch (presubmit_arch_executor)	3m 18s
arch (presubmit_arch_netbsd)	3m 48s
race	9m 51s
gvisor	3m 37s
	1h 9m 27s

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