Maven wants to access central.maven.org

Question

Since a few days, my maven build on gitlab (maven:3.6.3-jdk-11) tries to access central.maven.org and fails with

Caused by: org.eclipse.aether.transfer.ArtifactTransferException: Could not transfer artifact javax.media:jai_core:jar:1.1.3 from/to central.maven.org (http://central.maven.org/maven2): Transfer failed for http://central.maven.org/maven2/javax/media/jai_core/1.1.3/jai_core-1.1.3.jar
...
Caused by: java.net.UnknownHostException: central.maven.org: Name or service not known

I haven't changed the settings.xml. It looks like this:

...
<repositories>
    <repository>
          <id>central</id>
          <name>Central Repository</name>
          <url>https://repo1.maven.org/maven2/</url>
          <layout>default</layout>
          <snapshots>
            <enabled>false</enabled>
          </snapshots>
          <releases>
            <enabled>false</enabled>
            <updatePolicy>never</updatePolicy>
          </releases>
        </repository>
    </repositories>

<pluginRepositories>
    <pluginRepository>
      <id>central</id>
      <name>Central Repository</name>
      <url>https://repo1.maven.org/maven2/</url>
      <layout>default</layout>
      <snapshots>
        <enabled>false</enabled>
      </snapshots>
      <releases>
        <updatePolicy>never</updatePolicy>
      </releases>
    </pluginRepository>
</pluginRepositories>

...

That is, I haven't configured a lookup for central.maven.org. Even the maven super pom does not contain this url, according to https://maven.apache.org/ref/3.6.3/maven-model-builder/super-pom.html

Where does this come from and how can I fix this?