Remove unused feature from `sprs` dependency

[IvanIsCoding]

In short, this disables the alga feature of the sprs crate. It is enabled by default and we don't use those traits, so the code still compiles and our tests still pass.

It also solves the annoying issue of having a older num-complex in Cargo.lock, because sometimes cargo update swaps the version we use which causes issues with PyO3 and ndarray/NumPy.

[coveralls]

Pull Request Test Coverage Report for Build 11769424238

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 95.825%

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Totals
Change from base Build 11709175986:	0.0%
Covered Lines:	18016
Relevant Lines:	18801

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💛 - Coveralls