Fix avatars in percy not having the right border radius (#9102)

* Fix avatars in percy not having the right border radius

* Fix percy media for base avatars

Author: t3chguy

res/css/views/avatars/_BaseAvatar.pcss

@@ -55,9 +55,15 @@ limitations under the License.
 
 // Percy screenshot test specific CSS
 @media only percy {
-    .mx_BaseAvatar_initial,
-    .mx_BaseAvatar_initial + .mx_BaseAvatar_image {
-        // Stick the default room avatar colour, so it doesn't cause a false diff on the screenshot
+    // Stick the default room avatar colour, so it doesn't cause a false diff on the screenshot
+    .mx_BaseAvatar_initial {
         background-color: $username-variant2-color !important;
+        border-radius: 125px;
+    }
+    .mx_RoomAvatar_isSpaceRoom .mx_BaseAvatar_initial {
+        border-radius: 8px;
+    }
+    .mx_BaseAvatar_initial + .mx_BaseAvatar_image {
+        visibility: hidden;
     }
 }