[chore] add missing multiplier option to exporterhelper readme (#12776) #29416

Job	Run time
setup-environment	14s
govulncheck	28s
checks	2m 21s
unittest-matrix (ubuntu-latest, ~1.24)	6m 14s
unittest-matrix (ubuntu-latest, ~1.23)	6m 9s
lint	4m 34s
cross-build-collector (aix, ppc64)	41s
cross-build-collector (darwin, amd64)	41s
test-coverage	10m 52s
cross-build-collector (darwin, arm64)	43s
cross-build-collector (linux, 386)	48s
cross-build-collector (linux, amd64)	52s
cross-build-collector (linux, arm64)	42s
cross-build-collector (linux, ppc64le)	44s
cross-build-collector (linux, arm, 7)	44s
cross-build-collector (linux, s390x)	47s
cross-build-collector (windows, 386)	1m 9s
cross-build-collector (windows, amd64)	55s
unittest	1s
	39m 39s

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