[3.12] Docs: Use 'f-strings' as header (GH-112888) (#112923)

Docs: Use 'f-strings' as header (GH-112888)
(cherry picked from commit 5bf7580)

Co-authored-by: Hugo van Kemenade <hugovk@users.noreply.github.com>

Author: miss-islington

Doc/reference/lexical_analysis.rst

@@ -708,10 +708,12 @@ and formatted string literals may be concatenated with plain string literals.
    single: ! (exclamation); in formatted string literal
    single: : (colon); in formatted string literal
    single: = (equals); for help in debugging using string literals
+
 .. _f-strings:
+.. _formatted-string-literals:
 
-Formatted string literals
--------------------------
+f-strings
+---------
 
 .. versionadded:: 3.6