Bump avaje-jsonb.version from 1.4-RC1 to 1.4-RC6

Bumps `avaje-jsonb.version` from 1.4-RC1 to 1.4-RC6.

Updates `avaje-jsonb` from 1.4-RC1 to 1.4-RC6
- [Release notes](https://github.com/avaje/avaje-jsonb/releases)
- [Commits](https://github.com/avaje/avaje-jsonb/commits)

Updates `avaje-jsonb-generator` from 1.4-RC1 to 1.4-RC6

---
updated-dependencies:
- dependency-name: io.avaje:avaje-jsonb
  dependency-type: direct:development
- dependency-name: io.avaje:avaje-jsonb-generator
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

acceptance-tests/acceptance-tests-avaje-jsonb/pom.xml

@@ -31,7 +31,7 @@
   <description>Acceptance test components.</description>
 
   <properties>
-    <avaje-jsonb.version>1.4-RC1</avaje-jsonb.version>
+    <avaje-jsonb.version>1.4-RC6</avaje-jsonb.version>
     <jsonassert.version>1.5.1</jsonassert.version>
   </properties>