tools/syz-covermerger: fix misconfiguration #14766

Job	Run time
dashboard	3m 16s
aux	4m 54s
arch (presubmit_arch_linux)	10m 55s
build	11m 7s
arch (presubmit_arch_freebsd)	6m 32s
gvisor	4m 26s
old	6m 37s
arch (presubmit_arch_netbsd)	4m 32s
race	8m 32s
arch (presubmit_arch_openbsd)	4m 19s
arch (presubmit_arch_darwin)	4m 36s
race_dashboard	4m 10s
arch (presubmit_arch_windows)	3m 30s
arch (presubmit_arch_executor)	3m 31s
	1h 20m 57s

Provide feedback