Bugfix for method_params

[flowerthrower]

If a user specifies their own method_params for an optimizer, they are set correctly as the optimizer's attributes.
However, because of an elif mistake, the parameter was added to the unused_params dictionary even if they were used!
This leads to an error where we can have the same argument passed multiple times to spopt.minimize through the method_options argument.

[coveralls]

Pull Request Test Coverage Report for Build 8998248632

Details

• 0 of 1 (0.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 69.557%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/qutip_qtrl/optimizer.py	0	1	0.0%

Totals
Change from base Build 8976358348:	0.0%
Covered Lines:	3313
Relevant Lines:	4763

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💛 - Coveralls

[ajgpitch]

Seems a simple and correct fix