[Maven] Support 3.6.3 and 3.9.4 versions

[brandon-welsch]

https://maven.apache.org/docs/history.html

Currently the archives for these versions are not available in the bucket we use:

• https://lang-jvm.s3.us-east-1.amazonaws.com/maven-3.6.3.tar.gz
• https://lang-jvm.s3.us-east-1.amazonaws.com/maven-3.8.8.tar.gz

We should wait for it.

[Frzk]

There is also a 3.9.3 version (https://lang-jvm.s3.us-east-1.amazonaws.com/maven-3.9.3.tar.gz)

Anyway, it seems that upstream doesn't update this buildpack anymore and the packages are not available (as of july 2023).

[ipfaze]

It seems that upstream does still update this buildpack, they release V73 which use by default Maven 3.9.4. https://github.com/heroku/heroku-buildpack-java/commit/3424ddb215568d2ab5ccf4ca50dfb247d3a94419

As it was opened more than 6 months, I'm raising the priority from low to high.