fix(installer): Label field as username instead of login

[HB9HIL]

Summary

The intended username field in the installer is labeled "Login" which translates in many languages in a different meaning. It's better to label it Username.

Before:

After:

TODO

Nothing

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[joshtrichards]

Good catch, @HB9HIL

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[susnux]

Already implemented in #49962

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Thank you very much for your contribution, we hope you submit many more in the future :)