Dependabot ignore specific major by number

Hello, folks!
We are having some minor issues with dependabot when trying to ignore some major versions in gradle.
We have the following configuration:

version: 2
  - package-ecosystem: gradle
    directory: "/"
      interval: daily
    open-pull-requests-limit: 10
    target-branch: "main"
      - dependencies
      - dependency-name: "flyway-core"
        versions: [ "8.x" ]     

So that we keep getting upgrades from 7.x.

implementation "org.flywaydb:flyway-core:7.15.0"

However, we are still getting PRs to Bump flyway-core from 7.15.0 to 8.4.3.

I assume we could do something like update-types: ["version-update:semver-major"] but I still would like to have the version explicitly set since it helps with documenting in one single place.
Is there any problem with our syntax?