post-receive Script Update to use API Key instead of Crumb

[BatteryRage]

Update course content to change the post-receive file from using crumbs to using an API-key.

Change the code in post-receive from this:
crumb=$(curl -u "jenkins:1234" -s 'http://jenkins:8080/crumbIssuer/api/xml?xpath=concat(//crumbRequestField,":",//crumb)')
curl -u "jenkins:1234" -H "$crumb" -X POST http://jenkins:8080/job/maven-job/build?delay=0sec

To this:
curl -v -X POST http://jenkins:8080/job/maven-job/build?delay=0sec --user jenkins:<INSERT_API_KEY_HERE>

This works better with newer versions of Jenkins' default system settings because improved CSRF protection was implemented in version 2.176.2