fix highlight

Author: norareidy

source/usage-examples/findOne.txt

@@ -43,15 +43,15 @@ see the corresponding code for each runtime:
 
       .. literalinclude:: /includes/usage-examples/code-snippets/find-one-async.rs
          :language: rust
-         :emphasize-lines: 19
+         :emphasize-lines: 20
          :dedent:
 
    .. tab:: Synchronous
       :tabid: find-one-sync
 
       .. literalinclude:: /includes/usage-examples/code-snippets/find-one-sync.rs
          :language: rust
-         :emphasize-lines: 17
+         :emphasize-lines: 18
          :dedent:
 
 Output