update docstring

Author: araujoms

src/matmul.jl

@@ -575,7 +575,7 @@ end
 Computes syrk/herk for generic number types. If `conjugate` is false computes syrk, i.e.,
 ``A transpose(A) α + C β`` if `aat` is true, and ``transpose(A) A α + C β`` otherwise.
 If `conjugate` is true computes herk, i.e., ``A A' α + C β`` if `aat` is true, and
-``A' A α + C β`` otherwise.
+``A' A α + C β`` otherwise. Only the upper triangular is computed.
 """
 function generic_syrk!(C::StridedMatrix{T}, A::StridedVecOrMat{T}, conjugate::Bool, aat::Bool, α, β) where {T<:Number}
     require_one_based_indexing(C, A)