[Distributed] Fix swift-api-dump missing option
Resolves rdar://83727543
Without the fix we fail silly:
```
-> % ./utils/swift-api-dump.py ...
Traceback (most recent call last):
File "./utils/swift-api-dump.py", line 358, in <module>
main()
File "./utils/swift-api-dump.py", line 333, in main
if args.enable_experimental_distributed:
AttributeError: 'Namespace' object has no attribute 'enable_experimental_distributed'
```
