Jenkinsfile: aarch64: don't restrict to packet workers only

Pick whatever is available; packet worker, or auto-scaling
a1.xlarge arm64 machines on AWS

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

Jenkinsfile

@@ -762,7 +762,7 @@ pipeline {
                         beforeAgent true
                         expression { params.arm64 }
                     }
-                    agent { label 'aarch64 && packet' }
+                    agent { label 'aarch64' }
                     environment {
                         TEST_SKIP_INTEGRATION_CLI = '1'
                     }