Pipeline Git stage auto populating branch name and cred key with username and password

### Current Behavior

During a screenshare meeting with a customer, they set up a git stage and unwittingly saved it with autocompleted fields.


### Expected Behavior

no suggestions (or relevant suggestions)

Perhaps...
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If the above does not fettle this, then maybe `autocomplete="new-password"` will work?

### Steps To Reproduce

set up a git stage on a browser that offers suggestions

### Environment

- FlowFuse version: 2.16 FFC / live
- Node.js version:
- npm version:
- Platform/OS: Did not capture this information
- Browser: Did not capture this information

### Have you provided an initial effort estimate for this issue?

I have provided an initial effort estimate