Bump mail-api.version from 2.0.0-RC4 to 2.0.0-RC6

Bumps `mail-api.version` from 2.0.0-RC4 to 2.0.0-RC6.

Updates `jakarta.mail-api` from 2.0.0-RC4 to 2.0.0-RC6

Updates `mailapi` from 2.0.0-RC4 to 2.0.0-RC6
- [Release notes](https://github.com/eclipse-ee4j/mail/releases)
- [Commits](https://github.com/eclipse-ee4j/mail/commits)

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

pom.xml

@@ -31,7 +31,7 @@
     <jsp.api.version>5.0</jsp.api.version>
     <annotation-api.version>2.0.0-RC1</annotation-api.version>
     <transaction-api.version>2.0.0-RC1</transaction-api.version>
-    <mail-api.version>2.0.0-RC4</mail-api.version>
+    <mail-api.version>2.0.0-RC6</mail-api.version>
     <inject-api.version>2.0.0-RC4</inject-api.version>
     <infinispan.version>9.4.8.Final</infinispan.version>
     <hazelcast.version>4.0.1</hazelcast.version>