Remove min-height rule from CodeListing. (swiftlang#718)

This causes issues when code listings are used in `@Row`/`@Col` DocC
directives, because it results in them expanding beyond their normal
size and potentially obscures content below the row.

It doesn't seem that the `min-height` rule is still needed with the
recent updates to the styling of code listings whereas it was previously
used to fix an issue with overflow scrolling in tutorial code.

Resolves: rdar://112272083

src/components/ContentNode/CodeListing.vue

@@ -184,7 +184,6 @@ code {
 
 .code-listing {
   flex-direction: column;
-  min-height: 100%;
   border-radius: var(--code-border-radius, $border-radius);
   overflow: hidden;
   // we need to establish a new stacking context to resolve a Safari bug where