Update generic.jl (#1343)

```julia
julia> issymmetric(1)
true

julia> 1 isa AbstractMatrix
false
```

Author: WalterMadelim

src/generic.jl

@@ -1316,7 +1316,7 @@ issymmetric(A::AbstractMatrix{<:Real}) = ishermitian(A)
 """
     issymmetric(A) -> Bool
 
-Test whether a matrix is symmetric.
+Test whether a matrix or number is symmetric.
 
 # Examples
 ```jldoctest