travis.yml: don't tap anything. (#4705)
travis.yml: don't tap anything. (#4705)

These are immediately removed by test-bot because it's replicating end-user behaviour where we cannot set up dependent taps. If this breaks formulae they need dependencies to be fully scoped to e.g. `homebrew/versions/eigen32`.
parcollet/homebrew-science,quantumsteve/homebrew-science,andrewjpage/homebrew-science,heuermh/homebrew-science,philippbayer/homebrew-science,pditommaso/homebrew-science,DabeDotCom/homebrew-science,maplesond/homebrew-science,dpo/homebrew-science