Severe bug in LDA (default algorithm)

The default algorithm in this package is wrong. We cannot use symmetric to evaluate the eigenvalue decomposition of Sw^-1 Sb, because that multiplication is not guaranteed symmetric.

We should always be using pinv. There should be no other option.

References:

• https://gitlab.idiap.ch/bob/bob.learn.linear/-/blob/master/bob/learn/linear/include/bob.learn.linear/lda.h#L49
• https://gitlab.idiap.ch/bob/bob.learn.linear/-/blob/master/bob/learn/linear/cpp/lda.cpp#L137