SpringBoot Upgrade CI to Docker 26.1.2

Upgrade CI to Docker 26.1.2

Closes: https://github.com/spring-projects/spring-boot/issues/40768

Comment From: wilkinsona

Thanks, @PiyalAhmed, but as described in the PR template we prefer to deal with one-line version upgrades such as this ourselves. Also, we may just close #40768 as we're moving away from container-based CI on Concourse to GitHub Actions.

Comment From: PiyalAhmed

I see, thank you for pointing this out!