Update Doc/library/ast.rst

Co-authored-by: Stan Ulbrych <[email protected]>

Author: Yuki Kobayashi

Doc/library/ast.rst

@@ -1766,7 +1766,7 @@ Type annotations
 
 .. class:: TypeIgnore(lineno, tag)
 
-   A type ignore comment. ``lineno`` is the location of the ``#type ignore`` comment.
+   A type ignore comment. *lineno* is the location of the ``#type ignore`` comment.
    ``tag`` is the optional tag specified by the form ``#type ignore <tag>``.
 
    see :func:`ast.parse` for more details.