Update lexical_analysis.rst (GH-17508)


Use Sphinx role markup for `str.format`.

Automerge-Triggered-By: @csabella
(cherry picked from commit e2fb8a2c42ee60c72a40d93da69e9efc4e359023)

Co-authored-by: Géry Ogam <gery.ogam@gmail.com>
1 file changed