html2text: Skip generating footnotes for self-links.

Fixes the issue described at
https://www.wireshark.org/lists/wireshark-users/201912/msg00003.html

Change-Id: Ie3fd338ab1c6b216b05eeca002545868d3474bbb
Reviewed-on: https://code.wireshark.org/review/35426
Reviewed-by: Gerald Combs <gerald@wireshark.org>
Reviewed-by: Anders Broman <a.broman58@gmail.com>

tools/html2text.py

@@ -118,6 +118,10 @@ class TextHTMLParser(HTMLParser):
         elif self.skip_wrap:
             block = data
         else:
+            if self.href and data == self.href:
+                # This is a self link. Don't create a footnote.
+                self.href = None
+
             # For normal text, fold multiple whitespace and strip
             # leading and trailing spaces for the whole block (but
             # keep spaces in the middle).