refactor: Ignore Markdown anchors when setting backlink metadata on autorefs

The reason is that they don't appear in the table of contents, and therefore their URLs aren't collected for backlinking. Plus, they don't have titles so we'd have to record titles of headings above them. This is far from impossible, we might simply do that later.

Author: pawamoy

src/mkdocs_autorefs/_internal/backlinks.py

@@ -78,10 +78,7 @@ def run(self, root: Element) -> None:
 
     def _enhance_autorefs(self, parent: Element) -> None:
         for el in parent:
-            if el.tag == "a":  # Markdown anchor.
-                if not (el.text or el.get("href") or (el.tail and el.tail.strip())) and (anchor_id := el.get("id")):
-                    self._last_heading_id = anchor_id
-            elif el.tag in self._htags:  # Heading.
+            if el.tag in self._htags:
                 self._last_heading_id = el.get("id")
             elif el.tag == "autoref":
                 if "backlink-type" not in el.attrib: