Change date format, switch `$` to `%`

This was a typing mistake.

docs/courier-to-mailman3.md

@@ -25,3 +25,4 @@ This is our current version trying to communicate between courier and mailman3.
 * Now let's see if this works...
   * Date format set:
   * Level and File set in variable
+  * Format had errors with `$` used instead of `%`

source/courier-to-mailman3.py

@@ -17,7 +17,7 @@ logger = logging.getLogger(__name__)
 # Format time and message
 FORMAT = '%(asctime)s %(message)s'
 # Set Date Format
-DATEFMT = '%Y-$m-$d %H:%M:%S %Z'
+DATEFMT = '%Y-%m-%d %H:%M:%S %Z'
 LEVEL=logging.INFO
 LOGFILE='/opt/mailman/logs/courier-to-mailman.log'
 logging.basicConfig(filename=LOGFILE, level=LEVEL, format=FORMAT, datefmt=DATEFMT)