Restore default avatars on the index

stylesheets/manifest.css

@@ -204,8 +204,7 @@ button {
   .index img {
     height: 54px;
     width: 54px;
-    box-sizing: border-box;
+    background: #f3f3f3;
-    border: 27px #f3f3f3 solid;
     border-radius: 27px; }
   .index .message-list {
     display: none; }

stylesheets/view/_conversation.scss

@@ -291,9 +291,7 @@ button {
   img {
     height: 54px;
     width: 54px;
-    // delete next 2 lines
+    background: $grey_l;
-    box-sizing: border-box;
-    border: (54px / 2) $grey_l solid;
     border-radius: (54px / 2);
   }