dashboard/app: enable coverage pages formatting #16150

Job	Run time
build	1m 18s
aux	4m 10s
dashboard	1m 19s
arch (presubmit_arch_linux)	7m 3s
race_dashboard	1m 38s
arch (presubmit_arch_windows)	3m 33s
arch (presubmit_arch_netbsd)	3m 48s
arch (presubmit_arch_openbsd)	3m 52s
old	6m 52s
arch (presubmit_arch_executor)	3m 24s
arch (presubmit_arch_freebsd)	6m 8s
arch (presubmit_arch_darwin)	3m 50s
race	4m 37s
gvisor	3m 42s
	55m 14s

Provide feedback