[MPIR-481] clarify Java Version: build, target or release?

**[Hervé Boutemy](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=hboutemy)** opened **[MPIR-481](https://issues.apache.org/jira/browse/MPIR-481?redirect=false)** and commented

example: https://maven.apache.org/plugins-archives/maven-project-info-reports-plugin-3.9.0/summary.html
summary says "Java Version", which in this case means "Target/Release Java Version"
but it's written in a "Build" section, which may feel like "JDK used during build"

We should put the 2, as in MSHARED-1466 `META-INF/MANIFEST.MF` entries `Build-Jdk-Spec` vs `Release-Jdk-Spec`/`Target-Jdk-Spec`
= https://maven.apache.org/shared/maven-archiver/#manifest

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**Affects:** 3.8.0

**Issue Links:**
- [MSHARED-1466](https://issues.apache.org/jira/browse/MSHARED-1466) add default MANIFEST entry for release/target JDK

Start with the archived 3.9.0 summary example and the report's "Build" section, then read the Maven Archiver manifest documentation linked in the issue. Compare the Build-Jdk-Spec, Release-Jdk-Spec, and Target-Jdk-Spec terminology from MSHARED-1466. Done means the report distinguishes the JDK used during the build from the target or release Java version.

Written by the indexing model from the issue text.