Don't add fullname tag in 2GP package.xml (#3748)

Fixes #3415  for the scenario of when building a locked 2GP

Co-authored-by: David Reed <d.reed@salesforce.com>
Co-authored-by: James Estevez <jestevez@salesforce.com>

cumulusci/tasks/create_package_version.py

@@ -228,9 +228,7 @@ def _run_task(self):
         package_zip_builder = None
         with convert_sfdx_source(
             self.project_config.default_package_path,
-            None
-            if self.package_config.package_type == PackageTypeEnum.unlocked
-            else self.package_config.package_name,
+            None,
             self.logger,
         ) as path:
             package_zip_builder = MetadataPackageZipBuilder(