[CI-doc-daily] Remove RobertaPreLayernorm random tests
# What does this PR do?
Let's wait until #20757 is merged to merge this. 
The checkpoints for `RobertaPreLayerNormForMaskedLM`, `RobertaPreLayerNormForQuestionAnswering`, `RobertaPreLayerNormForTokenClassification`, where not provided thus the expected values are random and should not be tested. 
_The documentation is not available anymore as the PR was closed or merged._