The STS legacy project checker should be removed from the codebase. We don't need this anymore and we don't need to run this code and related jobs in STS anymore.

The code is mostly here: https://github.com/spring-projects/sts4/tree/main/eclipse-language-servers/org.springsource.ide.eclipse.commons.frameworks.ui/src/org/springsource/ide/eclipse/commons/frameworks/ui/internal/legacyconversion