dashboard/app: use machines with more memory for batch processing #16118

Job	Run time
build	14s
race	13s
gvisor	9s
arch (presubmit_arch_linux)	7s
race_dashboard	12s
arch (presubmit_arch_freebsd)	11s
aux	11s
dashboard	13s
arch (presubmit_arch_executor)	11s
arch (presubmit_arch_netbsd)	12s
arch (presubmit_arch_openbsd)	12s
old	11s
arch (presubmit_arch_darwin)	11s
arch (presubmit_arch_windows)	10s
	2m 37s

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