Remove IndexStyle specialization for AdjOrTransAbsMat (#55077)

Since `IndexStyle` falls back to `IndexCartesian` by default, this
specialization is unnecessary.

Author: jishnub

stdlib/LinearAlgebra/src/adjtrans.jl

@@ -327,7 +327,6 @@ size(A::AdjOrTransAbsMat) = reverse(size(A.parent))
 axes(v::AdjOrTransAbsVec) = (axes(v.parent,2), axes(v.parent)...)
 axes(A::AdjOrTransAbsMat) = reverse(axes(A.parent))
 IndexStyle(::Type{<:AdjOrTransAbsVec}) = IndexLinear()
-IndexStyle(::Type{<:AdjOrTransAbsMat}) = IndexCartesian()
 @propagate_inbounds Base.isassigned(v::AdjOrTransAbsVec, i::Int) = isassigned(v.parent, i-1+first(axes(v.parent)[1]))
 @propagate_inbounds Base.isassigned(v::AdjOrTransAbsMat, i::Int, j::Int) = isassigned(v.parent, j, i)
 @propagate_inbounds getindex(v::AdjOrTransAbsVec{T}, i::Int) where {T} = wrapperop(v)(v.parent[i-1+first(axes(v.parent)[1])])::T