don't deprecate collect, mention in docs

Author: dkarrasch

stdlib/LinearAlgebra/src/abstractq.jl

@@ -35,6 +35,7 @@ convert(::Type{AbstractQ{T}}, adjQ::AdjointQ{T}) where {T} = adjQ
 convert(::Type{AbstractQ{T}}, adjQ::AdjointQ) where {T} = convert(AbstractQ{T}, adjQ.Q)'
 
 # ... to matrix
+collect(Q::AbstractQ) = copyto!(Matrix{eltype(Q)}(undef, size(Q)), Q)
 Matrix{T}(Q::AbstractQ) where {T} = convert(Matrix{T}, Q*I) # generic fallback, yields square matrix
 Matrix{T}(adjQ::AdjointQ{S}) where {T,S} = convert(Matrix{T}, lmul!(adjQ, Matrix{S}(I, size(adjQ))))
 Matrix(Q::AbstractQ{T}) where {T} = Matrix{T}(Q)
@@ -44,7 +45,6 @@ convert(::Type{T}, Q::AbstractQ) where {T<:AbstractArray} = T(Q)
 # legacy
 @deprecate(convert(::Type{AbstractMatrix{T}}, Q::AbstractQ) where {T},
     convert(LinearAlgebra.AbstractQ{T}, Q))
-@deprecate(collect(Q::AbstractQ), copyto!(Matrix{eltype(Q)}(undef, size(Q)), Q))
 
 function size(Q::AbstractQ, dim::Integer)
     if dim < 1

stdlib/LinearAlgebra/src/qr.jl

@@ -379,7 +379,7 @@ Multiplication with respect to either full/square or non-full/square `Q` is allo
 and `F.Q*A` are supported. A `Q` matrix can be converted into a regular matrix with
 [`Matrix`](@ref). This operation returns the "thin" Q factor, i.e., if `A` is `m`×`n` with `m>=n`, then
 `Matrix(F.Q)` yields an `m`×`n` matrix with orthonormal columns.  To retrieve the "full" Q factor, an
-`m`×`m` orthogonal matrix, use `F.Q*I`. If `m<=n`, then `Matrix(F.Q)` yields an `m`×`m`
+`m`×`m` orthogonal matrix, use `F.Q*I` or `collect(F.Q)`. If `m<=n`, then `Matrix(F.Q)` yields an `m`×`m`
 orthogonal matrix.
 
 The block size for QR decomposition can be specified by keyword argument