wlc: print_html outputs API data without HTML escaping
### Impact
The HTML output format in wlc embeds API response data into HTML without escaping, allowing cross-site scripting when the output is rendered in a browser.
### Patches
*
https://github.com/WeblateOrg/wlc/pull/1327
### Workarounds
The only vulnerable code path is HTML output which is opt-in.
### References
Weblate thanks @fg0x0 for reporting this on GitHub.