samples com.google.cloud.libraries-bom are not updated automatically

[PhongChuong]

It seems to be pinned on 26.43.0 which is causing sample tests to fail the newly updated QueryJobOptional sample test

This has occurred previously in #3403 but it seems like the bot process was not fixed

[PhongChuong]

java-bigquery/renovate.json

Line 73 in e9e5b69

"/^com.google.cloud:libraries-bom/",

seems to be correct.

[PhongChuong]

Renovate bot is now updating the bom version.