BUG: Correct assignment in different versions of pandas

[bashtage]

Use iloc and reshaping to handle different version of pandas

• closes BUG/TST: recursive_ls test failures, pandas incompatibility #8775
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[josef-pkt]

As far as I could figure out it's pandas that broke this, not scipy
#8775

The optimization looks correct but for the linear and not the affine constraint

[bashtage]

Should be fixed now.