BugFix: Replace PDFPasswordIncorrect with PDFEncryptionWarning

[paulnawat]

Pull request

Thanks for improving pdfminer.six! Please include the following information to
help us discuss and merge this PR:

• A description of why this PR is needed. What does it fix? What does it
  improve?

  • From this PR htInEdin@10f6fb4#diff-19c70cd6ee74a06a40b8124e99c5da47009d4b7d3d08f588290052c7538f4d26L43, PDFPasswordIncorrect should be replaced by PDFEncryptionWarning.
  • This PR replaces the remaining PDFPasswordIncorrect with PDFEncryptionWarning

• A summary of the things that this PR changes.

  • PDFPasswordIncorrect no longer has any reference, when raised, resulting in

handle_action exception occurred. Error string: 'module 'pdfminer.pdfdocument' has no attribute 'PDFPasswordIncorrect''

• Reference the issues that this PR fixes (use the fixes #(issue nr) syntax).
  If this PR does not fix any issue, create the issue first and mention that
  you are willing to work on it.
  • PR htInEdin@10f6fb4#diff-19c70cd6ee74a06a40b8124e99c5da47009d4b7d3d08f588290052c7538f4d26L43

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide
instructions so we can reproduce. Include an example pdf if you have one.

Checklist

• I have added tests that prove my fix is effective or that my feature
  works
• I have added docstrings to newly created methods and classes
• I have optimized the code at least one time after creating the initial
  version
• I have updated the README.md or verified that this
  is not necessary
• I have updated the readthedocs documentation or
  verified that this is not necessary
• I have added a concise human-readable description of the change to
  CHANGELOG.md

[paulnawat]

From looking at the CHANGELOG, should we add/release 20211012 tag?

For more info, 20211012 is also available on pypi ( see https://pypi.org/project/pdfminer.six/)
However, looking at the RELEASE page, it's not released yet.

[pietermarsman]

Due to travis budgets our ci pipeline hasn't run in a while and that is how this bug crept in.

I prefer the fix in #704, where the exception class is introduced again.