Bump heroku/java to 0.3.15, heroku/java-function to 0.3.28

[Malax]

heroku/java 0.3.15

• Upgraded heroku/jvm to 0.1.14
• Upgraded heroku/maven to 0.2.6

heroku/java-function 0.3.28

• Upgraded heroku/jvm to 0.1.14
• Upgraded heroku/maven to 0.2.6

heroku/jvm 0.1.14

Changed

• Default version for OpenJDK 11 is now 11.0.14.1

Fixed

• JDK overlays (using the .jdk-overlay directory) are now properly applied

heroku/maven 0.2.6

• Switch to BSD 3-Clause License
• Applications that use Spring Boot are now properly detected even if their dependency to Spring Boot is transitive