remove trailing whitespace

[bastelfreak]

Please check the following items before submitting a PR -- thank you!

Note that this project is released with a Contributor Code of Conduct.
By participating in this project you agree to abide by its terms.
Contributor Code of Conduct.

• There is no existing PR that addresses this problem
• Mentioned any existing issues in your commit so they get linked and
  closed once this PR gets merged, i.e: Closes #1554 in the body of a commit
• Followed the instructions in the Contributing document
• Ran the unit/spec tests and ensured they still pass
• Added tests to cover the new behaviour
• Updated the documentation to match the changes
• When possible, add an entry to the CHANGELOG file
• Squashed your PR down to a single commit. You may forego this if the PR
  tries to address multiple issues. Though we prefer one PR per feature/fix,
  sometimes that's not feasible. In that case ensure that a single feature/fix
  and associated tests and documentation is bundled up in one commit

Optional, but extra points:

• Added tests to ensure the old behaviour cannot accidentally be
  reintroduced

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