Fix a JSON doc typo

Doc/library/json.rst

@@ -146,7 +146,7 @@ Basic Usage
    object members will be pretty-printed with that indent level.  An indent level
    of 0, negative, or ``""`` will only insert newlines.  ``None`` (the default)
    selects the most compact representation. Using a positive integer indent
-   indents that many spaces per level.  If *indent* is a string (such at '\t'),
+   indents that many spaces per level.  If *indent* is a string (such as ``"\t"``),
    that string is used to indent each level.
 
    If *separators* is an ``(item_separator, dict_separator)`` tuple, then it