Enable tools again

[marci543]

Failing tools are disabled in 80d4388.
Enable them again in #75, #76, #82.

ttc2018liveContest/.github/workflows/build.yml

Lines 13 to 16 in 80d4388

	# TODO: enable when ready
	rm docker/Dockerfile-differential
	rm docker/Dockerfile-graphblas
	rm docker/Dockerfile-neo4j

• Differential
• GraphBLAS
• Neo4j