Update lexical_analysis.rst (GH-17508)

Use Sphinx role markup for `str.format`.

Automerge-Triggered-By: @csabella

Doc/reference/lexical_analysis.rst

@@ -704,7 +704,7 @@ Top-level format specifiers may include nested replacement fields. These nested
 fields may include their own conversion fields and :ref:`format specifiers
 <formatspec>`, but may not include more deeply-nested replacement fields. The
 :ref:`format specifier mini-language <formatspec>` is the same as that used by
-the string .format() method.
+the :meth:`str.format` method.
 
 Formatted string literals may be concatenated, but replacement fields
 cannot be split across literals.