fix: added missing style for the flag

Signed-off-by: Roman Dmytrenko <[email protected]>

operations/import-export.mdx

@@ -86,7 +86,7 @@ flipt export --namespaces production
 </Tip>
 
 By default, Flipt exports resources in the _natural_ order of the selected storage type. While the output is typically consistent within the same storage type,
-import/export operations can yield varying results across different storage types. To enhance consistency during export, the --sort-by-key flag can be used.
+import/export operations can yield varying results across different storage types. To enhance consistency during export, the `--sort-by-key` flag can be used.
 
 ```yaml
 flipt export --sort-by-key --all-namespaces