changes based on Python review

shared/regex/codeql/regex/HostnameRegexp.qll

@@ -245,15 +245,11 @@ module Make<RegexTreeViewSig TreeImpl, HostnameRegexpSig<TreeImpl> Specific> {
     term.isRootTerm()
     or
     exists(RegExpTerm parent |
-      term = getLastChild(parent) and
+      term = parent.getLastChild() and
       isRightArmTerm(parent)
     )
   }
 
-  private RegExpTerm getLastChild(RegExpTerm parent) {
-    result = max(RegExpTerm child, int i | child = parent.getChild(i) | child order by i)
-  }
-
   /**
    * Holds if `regexp` is a regular expression that is likely to match a hostname,
    * but the pattern is incomplete and may match more hosts than intended.