Cleanup MarkdownLint issue in docs.

docs/user-guide/writing-your-docs.md

@@ -510,25 +510,25 @@ blocks without indentation.
 The first line should contain 3 or more backtick (`` ` ``) characters, and the
 last line should contain the same number of backtick characters (`` ` ``):
 
-~~~no-highlight
+````no-highlight
 ```
 Fenced code blocks are like Standard
 Markdown’s regular code blocks, except that
 they’re not indented and instead rely on
 start and end fence lines to delimit the
 code block.
 ```
-~~~
+````
 
 With this approach, the language can optionally be specified on the first line
 after the backticks which informs any syntax highlighters of the language used:
 
-~~~no-highlight
+````no-highlight
 ```python
 def fn():
     pass
 ```
-~~~
+````
 
 Note that fenced code blocks can not be indented. Therefore, they cannot be
 nested inside list items, blockquotes, etc.