dashboard/app: enable coverage pages formatting #16170

Job	Run time
aux	4m 10s
dashboard	2m 31s
build	2m 42s
race_dashboard	3m 28s
arch (presubmit_arch_freebsd)	6m 8s
arch (presubmit_arch_linux)	10m 25s
arch (presubmit_arch_netbsd)	3m 45s
arch (presubmit_arch_openbsd)	3m 44s
arch (presubmit_arch_executor)	3m 22s
arch (presubmit_arch_darwin)	3m 45s
arch (presubmit_arch_windows)	3m 35s
gvisor	3m 35s
old	6m 45s
race	9m 28s
	1h 7m 23s

Provide feedback