Overlay: remove now unused Overlay component

The Overlay component is not used in the create flow or anywhere else anymore since
USDC support was merged (PR #465), and is incompatible with the changes in the iOS
pointer-events bug fix (PR #470), where pointer-events were enabled on the overlay-frame
when they shouldn't. The incompatibility does not show directly anymore since PR #465 was
merged, but showed on the master branch before PR #465 that PR #470 was originally targeting.

src/request/create/index.html

@@ -81,7 +81,7 @@
     </div>
 
     <div id="app">
-        <div id="rotation-container" class="overlay-container">
+        <div id="rotation-container">
             <div id="intro" class="page nq-card">
                 <div class="page-header nq-card-header">
                     <a tabindex="0" class="page-header-back-button display-none">