GitHub block does not support fine-grained PATs

[EmilRex]

First check

• [X] I added a descriptive title to this issue.
• [X] I used the GitHub search to find a similar issue and didn't find it.
• [X] I searched the Prefect documentation for this issue.
• [X] I checked that this issue is related to Prefect and not one of its dependencies.

Bug summary

The GitHub storage block does not work with GitHub's new fine grained access tokens. Using a fine-grained token results in password prompt with the example below. More details in this SO post.

Reproduction

from prefect.filesystems import GitHub

GITHUB_TOKEN = "<PAT GOES HERE>"

block = GitHub(
    repository="https://github.com/<owner>/<repo>.git",
    reference="main",
    access_token=GITHUB_TOKEN
)

block.get_directory(local_path="./gh_pat_test")

Error

Password for 'https://<PAT GOES HERE>@github.com':

Versions

Version:             2.8.2
API version:         0.8.4
Python version:      3.9.16
Git commit:          afbed19d
Built:               Fri, Feb 17, 2023 10:02 AM
OS/Arch:             darwin/arm64
Profile:             default
Server type:         cloud

Additional context

No response

[serinamarie]

It sounds reasonable to me to support the new fine-grained PATs if possible 👍

[discdiver]

Closing as fine-grained PAT format is now shown in the UI with #8929 and confirmed with @zzstoatzz that it works.