ENG-48179: Revert NewClient api usage in configgrpc. #850

Job	Run time
setup-environment	51s
govulncheck	1m 6s
unittest-matrix (ubuntu-latest, ~1.22)	4m 38s
unittest-matrix (ubuntu-latest, ~1.21.11)	4m 47s
lint	2m 20s
checks	1m 46s
cross-build-collector (darwin, amd64)	44s
cross-build-collector (darwin, arm64)	40s
test-coverage	7m 56s
cross-build-collector (linux, 386)	39s
cross-build-collector (linux, amd64)	45s
cross-build-collector (linux, arm64)	48s
cross-build-collector (linux, ppc64le)	44s
cross-build-collector (linux, arm, 7)	43s
cross-build-collector (linux, s390x)	37s
cross-build-collector (windows, 386)	45s
cross-build-collector (windows, amd64)	46s
unittest	1s
	30m 36s

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