bpo-45421: Remove dead code from html.parser (GH-28847)

Support for HtmlParserError was removed back in 2014 with commit
73a4359, however this small block was
missed.

Lib/html/parser.py

@@ -328,13 +328,6 @@ def parse_starttag(self, i):
 
         end = rawdata[k:endpos].strip()
         if end not in (">", "/>"):
-            lineno, offset = self.getpos()
-            if "\n" in self.__starttag_text:
-                lineno = lineno + self.__starttag_text.count("\n")
-                offset = len(self.__starttag_text) \
-                         - self.__starttag_text.rfind("\n")
-            else:
-                offset = offset + len(self.__starttag_text)
             self.handle_data(rawdata[i:endpos])
             return endpos
         if end.endswith('/>'):