Fix some glitch-soc styling issues due to different class names

Partial fix to #1629

app/javascript/flavours/glitch/styles/containers.scss

@@ -44,7 +44,7 @@
 }
 
 .compose-standalone {
-  .compose-form {
+  .composer {
     width: 400px;
     margin: 0 auto;
     padding: 20px 0;

app/javascript/flavours/glitch/styles/contrast/diff.scss

@@ -1,17 +1,4 @@
 // components.scss
-.compose-form {
-  .compose-form__modifiers {
-    .compose-form__upload {
-      &-description {
-        input {
-          &::placeholder {
-            opacity: 1.0;
-          }
-        }
-      }
-    }
-  }
-}
 
 .rich-formatting a,
 .rich-formatting p a,

app/javascript/flavours/glitch/styles/rtl.scss

@@ -51,7 +51,7 @@ body.rtl {
     margin-left: 5px;
   }
 
-  .compose-form .compose-form__buttons-wrapper .character-counter__wrapper {
+  .composer .compose--counter-wrapper {
     margin-right: 0;
     margin-left: 4px;
   }