Change to optimize_for_target_gateset in docs

[dstrain115]

• This doc had an incorrect name for the function. Changed to the correct one.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 97.81%. Comparing base (da5c3b5) to head (d0b06eb).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #6658 +/- ## ======================================= Coverage 97.81% 97.81% ======================================= Files 1066 1066 Lines 91832 91832 ======================================= Hits 89826 89826 Misses 2006 2006 ```

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