revert master logo until june 3rd

app/ui/signupDialog.js

@@ -12,7 +12,10 @@ module.exports = function(trigger) {
       <send-signup-dialog
         class="flex flex-col lg:flex-row justify-center px-8 md:px-24 w-full h-full"
       >
-        <img src="${assets.get('master-logo.svg')}" class="h-16 mt-1 mb-4" />
+        <img
+          src="${assets.get('firefox_logo-only.svg')}"
+          class="h-16 mt-1 mb-4"
+        />
         <section
           class="flex flex-col flex-no-shrink self-center lg:mx-6 lg:max-w-xs"
         >