`flattenMode=oss` leaves `repositories`, contra docs

[jglick]

flatten-maven-plugin/src/main/java/org/codehaus/mojo/flatten/FlattenMode.java

Lines 40 to 44 in ec1c790

	/**
	* For Open-Source-Software projects that want to keep all {@link FlattenDescriptor optional POM elements} except
	* for {@link Model#getRepositories() repositories} and {@link Model#getPluginRepositories() pluginRepositories}.
	*/
	oss,

and

flatten-maven-plugin/src/main/java/org/codehaus/mojo/flatten/FlattenMojo.java

Lines 279 to 282 in ec1c790

	* <td>oss</td>
	* <td>For Open-Source-Software projects that want to keep all {@link FlattenDescriptor optional POM elements}
	* except for {@link Model#getRepositories() repositories} and {@link Model#getPluginRepositories()
	* pluginRepositories}.</td>

yet

flatten-maven-plugin/src/main/java/org/codehaus/mojo/flatten/FlattenMode.java

Lines 96 to 115 in ec1c790

	case oss:
	descriptor.setCiManagement(ElementHandling.expand);
	descriptor.setContributors(ElementHandling.expand);
	descriptor.setDistributionManagement(ElementHandling.expand);
	descriptor.setInceptionYear(ElementHandling.expand);
	descriptor.setIssueManagement(ElementHandling.expand);
	descriptor.setMailingLists(ElementHandling.expand);
	descriptor.setOrganization(ElementHandling.expand);
	descriptor.setPrerequisites(ElementHandling.expand);
	// $FALL-THROUGH$
	case ossrh:
	descriptor.setName(ElementHandling.expand);
	descriptor.setDescription(ElementHandling.expand);
	descriptor.setUrl(ElementHandling.expand);
	descriptor.setScm(ElementHandling.expand);
	descriptor.setDevelopers(ElementHandling.expand);
	// $FALL-THROUGH$
	case defaults:
	descriptor.setRepositories(ElementHandling.expand);
	break;

does not

descriptor.setRepositories(ElementHandling.remove);

as the docs imply. This can cause an error staging to Nexus:

Release repository is not allowed