Fix a bug that QuestionAnsweringPipeline ignores max_seq_len parameter
Author: wptoux
Pull request: yes

# What does this PR do?
Fix a bug that QuestionAnsweringPipeline ignores max_seq_len parameter

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Comments:
_The documentation is not available anymore as the PR was closed or merged._

Merging now since this PR is relatively trivial and was running for long enough, sorry about the review time.