Remove sampler_seed from spsa_grad

[lillian542]

Complete deprecation cycle for sampler_seed kwarg in spsa_grad

[github-actions]

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Please edit doc/releases/changelog-dev.md with:

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[lillian542]

[sc-43901]

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: -0.01% ⚠️

Comparison is base (273ddc6) 99.66% compared to head (9001eab) 99.66%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4550      +/-   ##
==========================================
- Coverage   99.66%   99.66%   -0.01%     
==========================================
  Files         376      376              
  Lines       33066    33059       -7     
==========================================
- Hits        32956    32949       -7     
  Misses        110      110              

Files Changed	Coverage Δ
pennylane/gradients/spsa_gradient.py	100.00% <ø> (ø)

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