Fix: patcher.py registry block passes wrong key to registry.patch

[mobs75]

Summary

In nuvolaris/patcher.py, the block guarded by if "registry" in what_to_do was incorrectly passing what_to_do['milvus'] to registry.patch() instead of what_to_do['registry'].

Root Cause

This is a copy-paste error from the adjacent milvus block. The guard condition correctly checks for "registry", but the dictionary access used the wrong key.

Impact

A KeyError: 'milvus' is raised in whisk_update whenever:

1. The diff contains spec.components.registry (registry is added or changed)
2. The diff does NOT contain spec.components.milvus (milvus is absent from last-handled-configuration or unchanged)

This silently breaks any platform update that touches the registry component without simultaneously touching milvus.

Fix

One-line change: replace what_to_do['milvus'] with what_to_do['registry'] in the registry block.

Testing

Verified by code inspection that all other what_to_do accesses in patcher.py correctly match their guard conditions. This block was the only mismatch.