Update html.parser.rst (GH-30678)

This PR for the documentation of the [html.parser](https://docs.python.org/3/library/html.parser.html) module will

- fix a terminology mistake (‘start of a tag’ -> ‘start tag of an element’);
- mention the parameter names of the `HTMLParser.handle_*` methods where missing.
(cherry picked from commit 2945f5a)

Co-authored-by: Géry Ogam <[email protected]>

Author: miss-islington

Doc/library/html.parser.rst

@@ -126,7 +126,7 @@ implementations do nothing (except for :meth:`~HTMLParser.handle_startendtag`):
 
 .. method:: HTMLParser.handle_starttag(tag, attrs)
 
-   This method is called to handle the start of a tag (e.g. ``<div id="main">``).
+   This method is called to handle the start tag of an element (e.g. ``<div id="main">``).
 
    The *tag* argument is the name of the tag converted to lower case. The *attrs*
    argument is a list of ``(name, value)`` pairs containing the attributes found