Do not spam Created directory to stderr on each get_filename4code

[Felixoid]

Hi. Each time the get_filename4code is called, it prints Created directory name, see timofurrer/pandoc-plantuml-filter#29 and timofurrer/pandoc-plantuml-filter#25

It will work as well, when the imagedir is symlink

In [3]: os.path.isdir('test-symlink')
Out[3]: True

In [6]: ls -l test-symlink
lrwxrwxrwx 1 felixoid felixoid 8 Jun 23 16:49 test-symlink -> examples/

[Felixoid]

I see it was changed in the 4da2c73

But now it's very noisy. The existing directory should be checked.

The job https://github.com/jgm/pandocfilters/actions/runs/9634327563/job/26569836419?pr=109 looks like some hick-up to me.

[Felixoid]

No, it's not a hick-up https://github.com/jgm/pandocfilters/actions/runs/9648939829/job/26611289299?pr=109

But it is something that needed to be addressed in the actions actions/setup-python#866

Specifically, actions/setup-python#866 (comment)