Update the Spring Boot version

[Buzzardo]

An ongoing task is to keep the Spring Boot version current in the build files:

To do so, update the following files:

complete/build.gradle
complete/pom.xml
initial/build.gradle
initial/pom.xml

[GeorgePanaretos]

Issued is resolved by:
1669a72

[Buzzardo]

Yes, it is. We leave one of these open all the time, though. As soon as the next patch release comes out, someone can fix this "issue" again. GitHub doesn't have an always-open issue mode.