Simplified Policy Optimization Objective as KL Divergence Minimization

In a derivation showing that a policy optimization objective is equivalent to minimizing KL divergence, the objective is simplified from arg min_θ E_{x~D} [ KL(π_θ(·|x) || π*(·|x)) - log Z(x) ] to arg min_θ E_{x~D} [ KL(π_θ(·|x) || π*(·|x)) ]. Why is it valid to remove the log Z(x) term during this final simplification?

A policy optimization objective can be shown to be equivalent to minimizing a KL divergence. Arrange the following expressions to show the correct logical sequence of this mathematical derivation, starting from the point where the optimal policy $\pi^*$ has been substituted into the objective.

Policy Optimization Derivation Step