Ensure LoginButton value text is displayed

[hannahblair]

Description

When initialising a LoginButton, we were hardcoding the button with the value "Sign in with Hugging Face". This changes that, so that self.value is used instead, which defaults to Sign in with Hugging Face if not provided.

Closes: #6772

Test:

import gradio as gr 

with gr.Blocks() as demo:
    gr.LoginButton(value="boop")

demo.launch()

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Install Gradio from this PR

pip install https://gradio-builds.s3.amazonaws.com/702e6b3525501907897e6b3f1a78e713617f20c5/gradio-4.9.1-py3-none-any.whl

Install Gradio Python Client from this PR

pip install "gradio-client @ git+https://github.com/gradio-app/gradio@702e6b3525501907897e6b3f1a78e713617f20c5#subdirectory=client/python"

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Ensure LoginButton value text is displayed

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[abidlabs]

This looks good @hannahblair -- could we also add a signed_in_value parameter as mentioned in: #6772 (comment)

[hannahblair]

@abidlabs Oh of course! That's done.

[abidlabs]

LGTM thanks @hannahblair for taking care of this!