remove some old files (why did we have travis anyway?) #551

Job	Run time
Julia 1.6 - ubuntu-latest - x64	4m 14s
Julia 1.6 - macOS-latest - x64	5m 10s
Julia 1.6 - windows-latest - x64	15m 32s
Julia 1 - ubuntu-latest - x64	4m 10s
Julia 1 - macOS-latest - x64	4m 46s
Julia 1 - windows-latest - x64	5m 2s
Julia nightly - ubuntu-latest - x64	4m 21s
Julia nightly - macOS-latest - x64	5m 47s
Julia nightly - windows-latest - x64	4m 55s
	53m 57s

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