pkg/symbolizer: Fix parser handling of small hex values #17573

Job	Run time
dashboard	2m 13s
race	10m 0s
arch (presubmit_arch_netbsd)	3m 46s
build	3m 20s
aux	4m 27s
arch (presubmit_arch_windows)	3m 28s
arch (presubmit_arch_openbsd)	3m 37s
arch (presubmit_arch_executor)	3m 20s
race_dashboard	2m 48s
arch (presubmit_arch_linux)	10m 29s
arch (presubmit_arch_darwin)	3m 42s
gvisor	4m 1s
arch (presubmit_arch_freebsd)	6m 20s
old	6m 56s
	1h 8m 27s

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