Ensure LoginButton `value` text is displayed (#6808)
* fix LoginButton value
* add changeset
* formatting
* add `signed_in_value` parameter
* tweak
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Co-authored-by: gradio-pr-bot <gradio-pr-bot@users.noreply.github.com>
Co-authored-by: Abubakar Abid <abubakar@huggingface.co>
