[FEATURE] Add links to the flavours page into the help message for the --flavour-name

### Summary

ewc hub deploy

### Motivation

Add links to the flavours page https://confluence.ecmwf.int/display/EWCLOUDKB/EWC+VM+plans into the help message for the --flavour-name

### Proposed Implementation

_No response_

### Alternatives Considered

_No response_

### Priority

None