Remove stray runtime and vendored artefacts #2

Job	Run time
conformance (fast-capability-matrix)	3m 10s
conformance (full-official)	5s
conformance (full-report)	6s
conformance (full-generated)	4s
conformance (fast-official)	1m 49s
conformance (full-artifacts)	4s
conformance (full-fixture-schema)	5s
conformance (fast-generated)	1m 54s
conformance (full-negative)	5s
conformance (weekly-community)	3s
conformance (fast-negative)	3m 13s
conformance (full-scenarios)	3s
trend-report	-1s
	10m 40s

Provide feedback