Exclude obsolete modules from Aggregator

[manandbytes]

$ mvn --file sources/aggregator/pom.xml validate
[INFO] Scanning for projects...
[ERROR] [ERROR] Some problems were encountered while processing the POMs:
[ERROR] Child module /sources/apache/maven/sources/aggregator/doxia/../../../doxia/tools/linkcheck of /sources/apache/maven/sources/aggregator/doxia/pom.xml does not exist @
[ERROR] Child module /sources/apache/maven/sources/aggregator/misc/../../../misc/plugin-testing/pom.xml of /sources/apache/maven/sources/aggregator/misc/pom.xml does not exist @
 @
[ERROR] The build could not read 2 projects -> [Help 1]
[ERROR]
[ERROR]   The project org.apache.maven.aggregator:doxia:1.0-SNAPSHOT (/sources/apache/maven/sources/aggregator/doxia/pom.xml) has 1 error
[ERROR]     Child module /sources/apache/maven/sources/aggregator/doxia/../../../doxia/tools/linkcheck of /sources/apache/maven/sources/aggregator/doxia/pom.xml does not exist
[ERROR]
[ERROR]   The project org.apache.maven.aggregator:misc:1.0-SNAPSHOT (/sources/apache/maven/sources/aggregator/misc/pom.xml) has 1 error
[ERROR]     Child module /sources/apache/maven/sources/aggregator/misc/../../../misc/plugin-testing/pom.xml of /sources/apache/maven/sources/aggregator/misc/pom.xml does not exist

• The Testing Framework is now part of Maven Core.
• Doxia LinkCheck library has been retired and is no longer maintained.

[Bukama]

The Testing Framework is now part of Maven Core.

Only for Maven 4.
Branch for Maven 3 still exists, see readme at https://github.com/apache/maven-plugin-testing

Doxia LinkCheck library has been retired and is no longer maintained.

I retired it in #45

[hboutemy]

there is a misunderstanding: https://github.com/apache/maven-plugin-testing
<project path='misc/plugin-testing' name='maven-plugin-testing.git' /> is not obsolete at all, be it for Maven 3 or 4

it seems there is confusion with <project path='core/3.x/its-3' name='maven-integration-testing.git' revision="maven-3.10.x" />

[hboutemy]

AFAIK, this PR can be closed as invalid