Printing for polynomials over the p-adic valuation rings misses parenthesis

[simonbrandhorst]

There should be parentheses

julia> K = qadic_field(3,3)[1]
Unramified extension of 3-adic numbers of degree 3

julia> R = valuation_ring(K)
Integers of Unramified extension of 3-adic numbers of degree 3

julia> Rt, t = polynomial_ring(R)
(Univariate polynomial ring in x over Integers of Unramified extension of 3-adic numbers of degree 3, x)

julia> t+3*t
3^0 + 3^1 + O(3^64)*x

[lgoettgens]

This looks like something similar to Nemocas/AbstractAlgebra.jl#1667. Let me try to see if the same fix works here as well.