Remove adding of trial param on auth failure in user sign in

What does this MR do and why?

Remove adding of trial param on auth failure in user sign in

• This was added in !15490 (diffs, comment 214397447) However, it was never used when frontend was implemented in !15289 (merged). This was meant to allow redirection of a user trial registration as seen for the sign up tab in !15289 (merged). We do not use a unified sign in/sign up page anymore, we use a separate endpoint for user registration(and trials). Since this was never used and even if it were, we don't need it anymore.
• we also to even more confirm do not see any instance of this param being passed in logs
• see more info in #13233 (closed) about why it was added.

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