Rename `trash (custom).svg` as electron doesn't like serving files with spaces

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

res/css/views/messages/_RedactedBody.scss

@@ -24,7 +24,7 @@ limitations under the License.
         height: 14px;
         width: 14px;
         background-color: $muted-fg-color;
-        mask-image: url('$(res)/img/feather-customised/trash (custom).svg');
+        mask-image: url('$(res)/img/feather-customised/trash.custom.svg');
         mask-repeat: no-repeat;
         mask-position: center;
         mask-size: contain;