lang/web: fix Emacs<26 incompatibility #806

The regexp argument for string-trim-right was introduced in 26.1.

modules/lang/web/+html.el

@@ -38,7 +38,10 @@
               (cl-loop for pair in (cdr alist)
                        unless (string-match-p "^[a-z-]" (cdr pair))
                        collect (cons (car pair)
-                                     (string-trim-right (cdr pair) "\\(?:>\\|]\\|}\\)+")))))
+                                     ;; TODO Replace with `string-trim-right' (Emacs 26+)
+                                     (if (string-match "\\(?:>\\|]\\|}\\)+\\'" string)
+                                         (replace-match "" t t string)
+                                       string)))))
     (setf (alist-get nil web-mode-engines-auto-pairs) nil))
 
   (map! :map web-mode-map