Remove nonexistent flag for acc offloading in memory_optimizations.rst

[janeyx99]

I forgot to remove mentions when I removed the flag in the last PR. -.-||

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[ebsmothers]

One nit, thanks for updating!

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 69.19%. Comparing base (27b0fcc) to head (48fef22).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1772      +/-   ##
==========================================
+ Coverage   67.38%   69.19%   +1.81%     
==========================================
  Files         305      305              
  Lines       15972    15952      -20     
==========================================
+ Hits        10762    11038     +276     
+ Misses       5210     4914     -296     

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