doc for gsl_blas_zher2k

[Brian Gough]

Mario Pernici writes:
 > Dear Sirs,
 >  there is a misprint in the manual
 >  C = \alpha A^H B + \alpha^* B^H A + \beta C when Trans is CblasTrans.
 >   becomes
 >  C = \alpha A^H B + \alpha^* B^H A + \beta C when Trans is CblasConjTrans.

Thanks for the documentation bug report -- now updated.

-- 
Brian