Update nexus staging maven plugin version

[dvacca-onfido]

Update nexus-staging-maven-plugin to avoid error:

Error:  Failed to execute goal org.sonatype.plugins:nexus-staging-maven-plugin:1.6.7:deploy (injected-nexus-deploy) on project onfido-api-java: Execution injected-nexus-deploy of goal org.sonatype.plugins:nexus-staging-maven-plugin:1.6.7:deploy failed: An API incompatibility was encountered while executing org.sonatype.plugins:nexus-staging-maven-plugin:1.6.7:deploy: java.lang.ExceptionInInitializerError: null

https://github.com/onfido/onfido-java/actions/runs/15022699142/job/42215925283