chore(buttons): make outline button background transparent

I was pairing with Sean over the `Banner` component and he pointed out that
the outline buttons have a white background when he intended for them to be
transparent. Currently, these buttons aren't being used anywhere, so I think
this is a safe change to make.

packages/components/src/Clickable/Clickable.module.css

@@ -147,14 +147,14 @@
 }
 
 .variantOutline {
-  background-color: var(--button-secondary-color);
+  background-color: transparent;
   border-color: var(--button-primary-color);
   color: var(--button-primary-color);
 
 
   &:focus,
   &.stateFocus {
-    background-color: var(--button-secondary-color);
+    background-color: transparent;
     color: var(--button-primary-color);
   }
 
@@ -165,7 +165,7 @@
   }
 
   &:disabled {
-    background-color: var(--button-secondary-color);
+    background-color: transparent;
     color: var(--button-primary-color);
   }
 }