update prometheus JAR MD5 hash in behave test for 0.12.0-8.el8_6

[jmtd]

    The md5 hash in the unit test is correct for the artefact we ship in RHEL7 :

-- md5: 8b3af39995b113baf35e53468bad7aae
-  target: jmx_prometheus_javaagent-0.3.2.redhat-00003.jar

I've just confirmed a scratch build with the new pnc stuff pulled in the right artefacts.

But the hash is not correct for UBI8 since we updated prometheus-jmx-exporter-0.12.0-8.el8_6.noarch
(it is now 1a9b7eb478c72028ca91e1bf6e40b48f).

So,

1. this is further evidence we should just turn off GHA for the rhel7 branch IMHO
2. we need to update the hash - but in the ubi8 branch, not here

Originally posted by @jmtd in https://github.com/jboss-container-images/openjdk/issues/329#issuecomment-1302163746