incorrect anchor in python3.9

# Documentation style bug

## Summary

bad anchor in glossary
## Actual style
python (3.9) glossary entry [f-string](https://devdocs.io/python~3.9/glossary#term-f-string) has a link to [formatted string literals](https://devdocs.io/python~3.9/reference/lexical_analysis#f-strings) with anchor `#f-strings` which doesn't scroll to any section because it's not present.

## Expected style

anchor `index-24` is needed to go to the correct section:
https://devdocs.io/python~3.9/reference/lexical_analysis#index-24

Start by locating the Python 3.9 glossary entry for f-string and its linked lexical_analysis section, using the URLs in the issue as entry points. Verify the current target anchor and update the link to index-24; done means the glossary link navigates to the formatted string literals section.

Scritto dal modello di indicizzazione a partire dal testo della issue.