Remove TwitterSignInHandler because its dependency TwitterKit is deprecated

[efrohnhoefer]

Closes: #1626

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[samtstern]

@efrohnhoefer thanks for sending this PR! I appreciate the effort however this is not the route we are going to take with Twitter. First we need to re-implement this on top of the "Generic IDP" flow (@lsirac can comment) and then we can remove this.

[samtstern]

This was fixed by @lsirac in #1714