Revert "Restrict binary ops for Diagonal and Symmetric to Number eltypes (#55251)"

This reverts commit 30573be.

Author: KristofferC

stdlib/LinearAlgebra/src/diagonal.jl

@@ -226,10 +226,10 @@ end
 (-)(Da::Diagonal, Db::Diagonal) = Diagonal(Da.diag - Db.diag)
 
 for f in (:+, :-)
-    @eval function $f(D::Diagonal{<:Number}, S::Symmetric)
+    @eval function $f(D::Diagonal, S::Symmetric)
         return Symmetric($f(D, S.data), sym_uplo(S.uplo))
     end
-    @eval function $f(S::Symmetric, D::Diagonal{<:Number})
+    @eval function $f(S::Symmetric, D::Diagonal)
         return Symmetric($f(S.data, D), sym_uplo(S.uplo))
     end
     @eval function $f(D::Diagonal{<:Real}, H::Hermitian)

stdlib/LinearAlgebra/test/diagonal.jl

@@ -1193,16 +1193,4 @@ end
     end
 end
 
-@testset "+/- with block Symmetric/Hermitian" begin
-    for p in ([1 2; 3 4], [1 2+im; 2-im 4+2im])
-        m = SizedArrays.SizedArray{(2,2)}(p)
-        D = Diagonal(fill(m, 2))
-        for T in (Symmetric, Hermitian)
-            S = T(fill(m, 2, 2))
-            @test D + S == Array(D) + Array(S)
-            @test S + D == Array(S) + Array(D)
-        end
-    end
-end
-
 end # module TestDiagonal