Improve flatten benchmark

[ajpotts]

Improve flatten benchmark by:

• Creating a new variable trimmed_N, so that N will not differ from pytest.N.
• Removes the flatten benchmark from the benchmark.ini, as it has been moved to the optional folder.
• Adds the shape_type to the benchmark.extra_info["description"].

[codecov]

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[drculhane]

Comment only, since what I'm about to point out is old code, not your change.

The multiple calls to np.sqrt, and the unneeded call to np.round, bother me. I would rewrite this as:

sqrt_N = int(np.sqrt(N))
trimmed_N = sqrt_N * sqrt_N
shape = (sqrt_N, sqrt_N)

But it certainly works as written, and one extra call to np.sqrt isn't going to noticeably affect the benchmark run time, so ... comment only.

Since this isn't meant to be something that requires resolution, feel free to resolve it yourself as you see fit.

[drculhane]

Nice fix. I left a comment, but it's purely a comment on the code that predates this change. It wasn't meant to require resolution.