tests: chang assertr of test_worker_mgr_rate_limiter #3199

Job	Run time
contrib-build (amd64)	33s
contrib-build (arm64)	49s
contrib-lint (contrib/nydusify)	1m 1s
contrib-unit-test-coverage	22s
contrib-build (ppc64le)	50s
contrib-lint (contrib/ctr-remote)	46s
contrib-lint (contrib/nydus-overlayfs)	36s
contrib-build (riscv64)	51s
nydus-build (amd64)	2m 13s
nydusd-build-macos (amd64)	2m 38s
nydus-build (arm64)	2m 14s
nydus-unit-test	5m 40s
nydus-build (ppc64le)	2m 3s
nydusd-build-macos (arm64)	3m 14s
nydus-build (riscv64)	2m 7s
cargo-deny	49s
nydus-unit-test-coverage	3m 51s
performance-test (fs-version-5)	1m 16s
performance-test (fs-version-6)	1m 9s
performance-test (zran)	1m 12s
nydus-integration-test	6m 40s
takeover-test	1m 48s
upload-coverage-to-codecov	9s
	42m 51s

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