Revert "Add perl as an explicit dependancy of erp5testnode"

This reverts commit 91168c430ce4412ba665d8ea8b9ae65e8ed2a04a.
Revert "increase slapos.libnetworkcache version, because slapos.recipe.build needs a recent version"

This reverts commit 51fb8ca190659b34eba01571abf7ab12e8a0d7ee.