Update help info for qr.jl (#55320)

'Rather than' seems to be the correct intent of the help info. This
would mean that Julia stores the result of QR in compact form instead of
(=rather than) storing in dense form.

'Rather as' would mean that Julia stores Q and R in two separate dense
matrices and not in compact form.

stdlib/LinearAlgebra/src/qr.jl

@@ -417,7 +417,7 @@ true
     `qr` returns multiple types because LAPACK uses several representations
     that minimize the memory storage requirements of products of Householder
     elementary reflectors, so that the `Q` and `R` matrices can be stored
-    compactly rather as two separate dense matrices.
+    compactly rather than two separate dense matrices.
 """
 function qr(A::AbstractMatrix{T}, arg...; kwargs...) where T
     require_one_based_indexing(A)