Rename "Attribute macros" section

This renames this section to follow the attribute template. Although I
like the old title, since it describes what it does, I would prefer to
not make exceptions and stay consistent.

Author: ehuss

src/procedural-macros.md

@@ -428,3 +428,17 @@ their equivalent `#[doc = r"str"]` attributes when passed to macros.
 [type expressions]: types.md#type-expressions
 [type]: types.md
 [union]: items/unions.md
+
+<script>
+(function() {
+    var fragments = {
+        "#attribute-macros": "procedural-macros.html#the-proc_macro_attribute-attribute",
+    };
+    var target = fragments[window.location.hash];
+    if (target) {
+        var url = window.location.toString();
+        var base = url.substring(0, url.lastIndexOf('/'));
+        window.location.replace(base + "/" + target);
+    }
+})();
+</script>