[cq] Removed unused polymer test data #91

Job	Run time
unit-tests (ubuntu-latest)	3m 58s
build-plugin	2m 40s
dart-analysis-server-tests (stable)	9m 24s
unit-tests (macos-latest)	3m 30s
verify-plugin (macos-latest)	3m 55s
verify-plugin (windows-latest)	13m 45s
verify-plugin (ubuntu-latest)	4m 58s
	42m 10s

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