Added password change for Letterboxd

[andylin2004]

Overall Checklist

• [x] I agree to the project's Developer Certificate of Origin
• [x] The top-level JSON objects are sorted alphabetically
• [x] There are no open pull requests for the same update

for change-password-URLs.json

• [x] There is no Well-Known URL for Changing Passwords (https://example.com/.well-known/change-password)
• [x] The URL either makes the experience better or no worse than being directed to just the domain in a non-logged-in state

[rmondello]

Thanks @andylin2004!