Remove tests for displays

test/displays.jl

-using Test
-
-using KM3io
-using KM3NeTTestData
-
-const ONLINEFILE = datapath("online", "km3net_online.root")
-const OFFLINEFILE = datapath("offline", "km3net_offline.root")
-
-@testset "displays" begin
-    f = ROOTFile(OFFLINEFILE)
-    open(tempname(), "w") do io
-        show(io, f.offline[1])  # Evt
-        show(io, MIME"text/plain"(), f.offline[1])  # Evt
-        show(io, f.offline[1:4])  # compact Evt
-        show(io, f.offline[1].trks)  # Trks
-        show(io, f.offline[1].trks[1:4])  # compact Trks
-    end
-end