Test-requirements.txt uses differnt version of pl-bolts than main environment

[ant0nsc]

We seem to be overwriting core packages in the InnerEye environment with ones specified in test-requirements.txt. For example, we have conflicting versions of lightning-bolts (0.4.0 and 0.5.0)

test-requirements should be what it says on the tin: only stuff that we need for running the test pipeline. At present, we have things like opencv there.

AB#5165