Paketo buildpacks have started logging a deprecation warning when the API version support advertised by the platform is less than 0.8. Since Spring Boot 2.6.x advertises support for platform API 0.5, the 2.6.x system tests fail when the tests detect the deprecation warning in the build output. The 2.7.x and later system tests pass because they advertise platform API version 0.8.
The 2.6.x Paketo system tests should ignore build output deprecation warnings, but the 2.7.x and later tests can fail on deprecation warnings.