Consistently use T for separating date and time in ISO 8601 datetime examples

Author: notatallshaw

docs/html/user_guide.rst

@@ -322,7 +322,7 @@ packages that were available at a known point in time.
 The option accepts ISO 8601 datetime strings in several formats:
 
 * ``2025-03-16`` - Date in local timezone
-* ``2025-03-16 12:30:00`` - Datetime in local timezone
+* ``2025-03-16T12:30:00`` - Datetime in local timezone
 * ``2025-03-16T12:30:00Z`` - Datetime in UTC
 * ``2025-03-16T12:30:00+05:00`` - Datetime in UTC offset