Revert "Fix iframe hiding to avoid breaking stl, pdb, and images"

This reverts commit bc864c3.

Author: felliott

mfr/server/static/css/mfr.css

@@ -42,16 +42,14 @@ This CSS was stripped out of base.css from the osf-style repo.
     align-items: center;
     width: 100%;
     height: 250px;
-    top: 0;
-    left: 0;
 }
 
 .embed-responsive-pdf {
     padding-bottom: 95%;
 }
 
 #mfrIframe iframe {
-    opacity: 0.0;
+    display: none;
 }
 
 #mfrIframe {

mfr/server/static/js/mfr.js

@@ -82,7 +82,7 @@
             self.pymParent.el.appendChild(self.spinner);
             $(self.pymParent.iframe).on('load', function() {
                 self.pymParent.el.removeChild(self.spinner);
-                this.style.opacity = "1.0"
+                this.style.display = "block"
             })
 
             self.pymParent.onMessage('embed', function(message) {