remove legacy STS project checker

[martinlippert]

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

[BoykoAlex]

What about workspace conversion in org.springsource.ide.eclipse.commons.frameworks.core.legacyconversion package of plugin project org.springsource.ide.eclipse.commons.frameworks.core? Convert 2.x workspace into 3.x - think this long gone now... I'd remove this as well... Workspace conversion is some old preference roo, grails etc conversions.

[BoykoAlex]

Removed legacy conversion code for both project and workspace: 2b85fb3