Update example pull command version number

Author: andrewnicols

README.md

@@ -35,7 +35,7 @@ A Moodle PHP environment configured for Moodle development based on [Official PH
 ## Example usage
 The following command will expose the current working directory on port 8080:
 ```bash
-$ docker run --name web0 -p 8080:80  -v $PWD:/var/www/html moodlehq/moodle-php-apache:7.1
+$ docker run --name web0 -p 8080:80  -v $PWD:/var/www/html moodlehq/moodle-php-apache:8.3
 ```
 
 ## Features