Bug/4823 upload file with leading space

[robinmolen]

Closes #4823

Changes

When uploading a file with a leading space, the website will show a descriptive error message.

Checklist

Check off the items that are completed or not relevant.

• Impact on features

  • [X] Checked copying a form
  • [X] Checked import/export of a form
  • [X] Config checks in the configuration overview admin page
  • [X] Problem detection in the admin email digest is handled

• Release management

  • [X] I have labelled the PR as "needs-backport" accordingly

• I have updated the translations assets (you do NOT need to provide translations)

  • [X] Ran ./bin/makemessages_js.sh
  • [X] Ran ./bin/compilemessages_js.sh

• Commit hygiene

  • [X] Commit messages refer to the relevant Github issue
  • [X] Commit messages explain the "why" of change, not the how

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 96.56%. Comparing base (4b73a1d) to head (d50482a). Report is 15 commits behind head on master.

Files with missing lines	Patch %	Lines
src/openforms/formio/components/vanilla.py	0.00%	1 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #4830 +/- ## ========================================== - Coverage 96.57% 96.56% -0.01% ========================================== Files 747 747 Lines 25400 25402 +2 Branches 3355 3356 +1 ========================================== Hits 24529 24529 - Misses 608 609 +1 - Partials 263 264 +1 ```

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[robinmolen]

Closed this PR in favor of #4833