MINOR: code cleanup GroupMetadataManagerTestContext (#19554) #119

Job	Run time
build / Configure Workflow	2s
build / Load Test Catalog	33s
build / Compile and Check (Merge Ref)	12m 37s
build / CI checks completed	3s
build / Collate Test Catalog	0s
build / JUnit tests Java ${{ matrix.java }}${{ matrix.run-flaky == true && ' (flaky)' \|\| '' }}${{ matrix.run-new == true && ' (new)' \|\| '' }}	-1s
build / Update Test Catalog	0s
	13m 14s

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