[docs] change docstring to match code (#55013)

The docstring of `LinearAlgebra.reflectorApply!` is incorrect. It says
the function is applying `(I - τ*[1; x] * [1; x]')*A`, but in reality it
is applying `(I - conj(τ)*[1; x[2:end]]*[1; x[2:end]]')*A`. You can
check that by looking at the code, or running for example
```julia
using LinearAlgebra
T=ComplexF64;d=5;
τ=randn(T);x=randn(T,d);A=randn(T,d,d);
(I - conj(τ)*[1; x[2:end]]*[1; x[2:end]]')*A
LinearAlgebra.reflectorApply!(x,τ,A)
```

(cherry picked from commit 1ece299)

stdlib/LinearAlgebra/src/generic.jl

@@ -1607,7 +1607,7 @@ end
 """
     reflectorApply!(x, τ, A)
 
-Multiplies `A` in-place by a Householder reflection on the left. It is equivalent to `A .= (I - τ*[1; x] * [1; x]')*A`.
+Multiplies `A` in-place by a Householder reflection on the left. It is equivalent to `A .= (I - conj(τ)*[1; x[2:end]]*[1; x[2:end]]')*A`.
 """
 @inline function reflectorApply!(x::AbstractVector, τ::Number, A::AbstractVecOrMat)
     require_one_based_indexing(x)