Revert "Theme Support with a Dark Mode (#974)" (#1011)

This reverts commit cf24113924.

src/images/loading-white.svg

@@ -1,6 +0,0 @@
-<svg xmlns="http://www.w3.org/2000/svg" width="100%" height="100%" viewBox="0 0 100% 100%">
-  <text fill="#fbfbfb" x="50%" y="50%" font-family="\'Open Sans\', \'Helvetica Neue\', Helvetica, Arial, sans-serif"
-        font-size="18" text-anchor="middle">
-    Loading...
-  </text> 
-</svg>

src/images/loading.svg

@@ -1,6 +1,6 @@
 <svg xmlns="http://www.w3.org/2000/svg" width="100%" height="100%" viewBox="0 0 100% 100%">
-  <text fill="#333333" x="50%" y="50%" font-family="\'Open Sans\', \'Helvetica Neue\', Helvetica, Arial, sans-serif"
+  <text fill="%23333333" x="50%" y="50%" font-family="\'Open Sans\', \'Helvetica Neue\', Helvetica, Arial, sans-serif"
         font-size="18" text-anchor="middle">
     Loading...
   </text>
-</svg>
+</svg>