*: always backquote stdin, stdout and stderr (#9584)

pages/osx/base64.md

@@ -11,10 +11,10 @@
 
 `base64 --decode --input={{base64_file}}`
 
-- Encode from stdin:
+- Encode from `stdin`:
 
 `echo -n "{{plain_text}}" | base64`
 
-- Decode from stdin:
+- Decode from `stdin`:
 
 `echo -n {{base64_text}} | base64 --decode`