Fix mvn release for versioned artifact

The `mvn release:prepare` failed with
```
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-shade-plugin:3.2.1:shade (default) on project kryo5: Error creating shaded jar: /path/to/kryo/target/kryo-5.0.0-RC5.jar (No such file or directory)
```
because release:prepare invoked clean when building the versioned (kryo5) module.

To fix this, for the maven release plugin the `preparationGoals`
are overridden, to only invoke `verify` (default is `clean verify`).

When running a release, `clean` of course has to be run manually at first.

pom.xml

@@ -126,6 +126,18 @@
 					<artifactId>findbugs-maven-plugin</artifactId>
 					<version>3.0.5</version>
 				</plugin>
+
+				<plugin>
+					<groupId>org.apache.maven.plugins</groupId>
+					<artifactId>maven-release-plugin</artifactId>
+					<configuration>
+						<!-- Don't run clean, because this would delete the kryo artifact, which would fail the shade plugin
+						    because the kryo jar would no longer exist.
+						    https://maven.apache.org/maven-release/maven-release-plugin/prepare-mojo.html#preparationGoals
+						-->
+						<preparationGoals>verify</preparationGoals>
+					</configuration>
+				</plugin>
 			</plugins>
 		</pluginManagement>
 	</build>