image regression test timeout

[andiwand]

the image regression test in the CI times out for very big files like efficiency+style-big-1.ods

possible solutions

• limit render view with max width / max height

references

• https://github.com/opendocument-app/OpenDocument.core/pull/243/checks?check_run_id=2123864766
• https://github.com/opendocument-app/OpenDocument.core/pull/243#issuecomment-800470328

[andiwand]

using firefox for rendering fixed the problem