doc: unify spaces in a querystring.md code example

PR-URL: https://github.com/nodejs/node/pull/12465
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>

doc/api/querystring.md

@@ -101,7 +101,7 @@ For example:
 querystring.stringify({ foo: 'bar', baz: ['qux', 'quux'], corge: '' })
 // returns 'foo=bar&baz=qux&baz=quux&corge='
 
-querystring.stringify({foo: 'bar', baz: 'qux'}, ';', ':')
+querystring.stringify({ foo: 'bar', baz: 'qux' }, ';', ':')
 // returns 'foo:bar;baz:qux'
 ```