Bump idna from 3.13 to 3.15

Bumps [idna](https://github.com/kjd/idna) from 3.13 to 3.15.
- [Release notes](https://github.com/kjd/idna/releases)
- [Changelog](https://github.com/kjd/idna/blob/master/HISTORY.md)
- [Commits](kjd/idna@v3.13...v3.15)

---
updated-dependencies:
- dependency-name: idna
  dependency-version: '3.15'
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

requirements.txt

@@ -18,7 +18,7 @@ filetype==1.2.0
     # via lektor
 flask==2.3.3
     # via lektor
-idna==3.13
+idna==3.15
     # via requests
 inifile==0.4.1
     # via lektor