dashboard/app: always gzip intermediate handler results #15451

Job	Run time
aux	3m 45s
build	2m 35s
arch (presubmit_arch_linux)	9m 18s
dashboard	2m 52s
arch (presubmit_arch_freebsd)	5m 39s
race	9m 46s
arch (presubmit_arch_netbsd)	3m 32s
arch (presubmit_arch_openbsd)	3m 33s
gvisor	3m 13s
arch (presubmit_arch_darwin)	3m 30s
arch (presubmit_arch_windows)	3m 13s
old	6m 9s
arch (presubmit_arch_executor)	3m 9s
race_dashboard	3m 56s
	1h 4m 10s

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