Update doc for deno fmt --no-semicolons arg. (#21414)

Include default, like other bools.

---------

Signed-off-by: John Spurlock <47259736+johnspurlock-skymethod@users.noreply.github.com>

cli/args/flags.rs

@@ -1654,7 +1654,9 @@ Ignore formatting a file by adding an ignore comment at the top of the file:
             .value_parser(value_parser!(bool))
             .default_missing_value("true")
             .require_equals(true)
-            .help("Don't use semicolons except where necessary."),
+            .help(
+              "Don't use semicolons except where necessary. Defaults to false.",
+            ),
         )
     })
 }