[Glitch] Increase contrast of upload progress background

Port f4f91bc295 to glitch-soc

Signed-off-by: Claire <claire.github-309c@sitedethib.com>

app/javascript/flavours/glitch/styles/components/compose_form.scss

@@ -535,7 +535,7 @@
   border-radius: 6px;
   width: 100%;
   height: 6px;
-  background: $ui-base-lighter-color;
+  background: darken($simple-background-color, 8%);
 }
 
 .upload-progress__tracker {

app/javascript/flavours/glitch/styles/mastodon-light/diff.scss

@@ -258,6 +258,10 @@ html {
   border-color: $ui-base-color;
 }
 
+.upload-progress__backdrop {
+  background: $ui-base-color;
+}
+
 // Change the background colors of statuses
 .focusable:focus {
   background: $ui-base-color;