Update login form parameters to match new identifiers on site

[felddy]

🗣 Description

The FoundryVTT web site login changed the name of the fields in the login form. This broke authentication.
This PR changes the names of the posted fields to match the new form's expectations.

💭 Motivation and context

Notified of

See:

• Foundry website login change broke authentication helper utility #868
• Unable to authenticate with secrets or environment variables #867

Closes #868

🧪 Testing

Tested in node via CLI and in continuous integration.

✅ Pre-approval checklist

• This PR has an informative and human-readable title.
• Changes are limited to a single goal - eschew scope creep!
• All relevant type-of-change labels have been added.
• I have read the CONTRIBUTING document.
• These code changes follow cisagov code standards.
• All relevant repo and/or project documentation has been updated
  to reflect the changes in this PR.
• All new and existing tests pass.