Auto merge of #18092 - cbrewster:ce_domtokenlist, r=<try>

Only run DOMTokenList update steps if token was found

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components/script/dom/domtokenlist.rs

@@ -158,9 +158,9 @@ impl DOMTokenListMethods for DOMTokenList {
             } else {
                 atoms.remove(pos);
             }
+            // Step 5.
+            self.element.set_atomic_tokenlist_attribute(&self.local_name, atoms);
         }
-        // Step 5.
-        self.element.set_atomic_tokenlist_attribute(&self.local_name, atoms);
         Ok(())
     }