Bug 1576230 - class should be className in UserAgentInput. r=bradwerth

Differential Revision: https://phabricator.services.mozilla.com/D43274

--HG--
extra : moz-landing-system : lando

devtools/client/responsive/components/UserAgentInput.js

@@ -76,7 +76,7 @@ class UserAgentInput extends PureComponent {
       "UA:",
       dom.input({
         id: "user-agent-input",
-        class: "text-input",
+        className: "text-input",
         onChange: this.onChange,
         onKeyUp: this.onKeyUp,
         placeholder: getStr("responsive.customUserAgent"),