java: add logging-logback to gapic-libraries-bom/pom.xml

[zhumin8]

Add it similar to legacy BOMs here:

librarian/internal/librarian/java/postgenerate.go

Line 63 in 3c46b73

dnsBOM = legacyBOM{"java-dns", "com.google.cloud", "google-cloud-dns"}

This is needed per Java team request. This was attempted directly adding to the generated pom.xml in googleapis/google-cloud-java#13663, which causes generation diff: googleapis/google-cloud-java#13672

[zhumin8]

For what it worth, #6648 introduces a comment in the generated pom.xml files, hopefully can avoid similar changes to the generated file in the future.

[zhumin8]

One other thought, porting from chat:
What I am trying to get to is, as you can see, there are a few outliers hardcoded in librarian right now (see code), with assumption that these are legacy ones and hardly change. If you anticipate more additions to this bom in the future, I think we can switch this to be configurable via librarian.yaml

cc. .@blakeli0 @lqiu96 @JoeWang1127