highlight: don't include scope in ScopeEnd events

When there are embedded documents, multiple scopes can start or
end at the same position. Previously, there was no guarantee that
the ScopeEnd events would always occur in the reverse order of the
ScopeStart events. The easiest way to avoid exposing inconsistency
is to not surface the scopes being ended.

cli/src/highlight.rs

@@ -209,7 +209,7 @@ pub fn ansi(
             HighlightEvent::ScopeStart(s) => {
                 scope_stack.push(s);
             }
-            HighlightEvent::ScopeEnd(_) => {
+            HighlightEvent::ScopeEnd => {
                 scope_stack.pop();
             }
         }

cli/src/tests/highlight_test.rs

@@ -162,8 +162,7 @@ fn to_token_vector<'a>(
     )? {
         match event {
             HighlightEvent::ScopeStart(s) => scopes.push(s),
-            HighlightEvent::ScopeEnd(s) => {
-                assert_eq!(*scopes.last().unwrap(), s);
+            HighlightEvent::ScopeEnd => {
                 scopes.pop();
             }
             HighlightEvent::Source(s) => {