there are no tests for Julia

Bug description

As far as I can tell, there are no tests of rendering .qmd files with Julia code. E.g.

paul@pts2 tests  [main] $ grep -rnw . -e "{julia}" | wc -l
0
paul@pts2 tests  [main] $ grep -rnw . -e "{python}" | wc -l
15
paul@pts2 tests  [main] $ grep -rnw . -e "{r}" | wc -l
130

Checklist

• Please include a minimal, fully reproducible example in a single .qmd file? Please provide the whole file rather than the snippet you believe is causing the issue.
• Please format your issue so it is easier for us to read the bug report.
• Please document the RStudio IDE version you're running (if applicable), by providing the value displayed in the "About RStudio" main menu dialog?
• Please document the operating system you're running. If on Linux, please provide the specific distribution.

Start by running the issue's grep searches in the tests tree to compare {julia} coverage with {python} and {r}. Add a minimal .qmd rendering test for Julia code, and consider the work done when Julia rendering has test coverage comparable to the existing language tests.