spring-boot update to 2.3.3+

[hohwille]

As a devon4j user, I want to get new apps based on recent technology-stack so that I start a new project on recent libs rather than having known bugs and CVEs from the beginning leading to technical debt.

Current spring-boot version is 2.2.7.RELEASE:

devon4j/pom.xml

Line 32 in b540a8e

<spring.boot.version>2.2.7.RELEASE</spring.boot.version>

Latest available version is 2.3.3.RELEASE:
https://repo1.maven.org/maven2/org/springframework/boot/spring-boot-dependencies/

[hohwille]

I ran the security check (OWASP dependency check) on our latest archetype (without this PR applied) and got:

spring-security-core-5.3.4.RELEASE.jar (pkg:maven/org.springframework.security/spring-security-core@5.3.4.RELEASE, cpe:2.3:a:pivotal_software:spring_security:5.3.4.release:*:*:*:*:*:*:*, cpe:2.3:a:security-framework_project:security-framework:5.3.4.release:*:*:*:*:*:*:*) : CVE-2018-1258