chore: remove no longer relevant legacy signin example

[filmaj]

No description provided.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.83%. Comparing base (45bdb8d) to head (2d39ab7).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2092   +/-   ##
=======================================
  Coverage   91.83%   91.83%           
=======================================
  Files          38       38           
  Lines       10263    10263           
  Branches      646      646           
=======================================
  Hits         9425     9425           
  Misses        826      826           
  Partials       12       12           

Flag	Coverage Δ
cli-hooks	95.23% <ø> (ø)
cli-test	95.69% <ø> (ø)
oauth	77.39% <ø> (ø)
socket-mode	58.22% <ø> (ø)
web-api	96.88% <ø> (ø)
webhook	96.65% <ø> (ø)

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