add avaje-jsonb-parent 3.0-RC6

[hboutemy]

https://github.com/jvm-repo-rebuild/reproducible-central/blob/master/content/io/avaje/jsonb/README.md

[github-actions]

• content/io/avaje/jsonb/avaje-jsonb-3.0-RC6.buildspec io.avaje:avaje-jsonb

version=3.0-RC6
ok=22
ko=0
ignored=0
koFiles=""
ignoredFiles=""
reference_java_version="21 (from MANIFEST.MF Build-Jdk-Spec)"

docker build -q -t ghcr.io/jvm-repo-rebuild/rb-ubuntu-jdk21-toolchains-21
	1:00.78 real,	0.13 user,	0.11 sys
docker build -q -t ghcr.io/jvm-repo-rebuild/rb-ubuntu-jdk21-toolchains-21-maven-3.6.3
	0:09.62 real,	0.06 user,	0.05 sys
docker build -q -t ghcr.io/jvm-repo-rebuild/rb-ubuntu-jdk21-toolchains-21-maven-3.6.3-runner
	0:12.37 real,	0.07 user,	0.06 sys
docker build -q -t ghcr.io/jvm-repo-rebuild/rb-ubuntu-jdk21-toolchains-21-maven-3.6.3-runner-utc-en_us-0002
	0:15.34 real,	0.06 user,	0.07 sys
docker run --name rebuild-central --rm
	0:19.93 real,	0.02 user,	0.07 sys