Remove unused variable.

Change-Id: Ic8de7931be8ac51f583eaa5da73178aa0a38122b

internal/ceres/polynomial_solver.cc

diff --git a/internal/ceres/polynomial_solver.cc b/internal/ceres/polynomial_solver.cc
index 8782eda..027493a 100644
--- a/internal/ceres/polynomial_solver.cc
+++ b/internal/ceres/polynomial_solver.cc
@@ -122,8 +122,6 @@
 bool FindPolynomialRoots(const Vector& polynomial_in,
                          Vector* real,
                          Vector* imaginary) {
-  const double epsilon = std::numeric_limits<double>::epsilon();
-
   if (polynomial_in.size() == 0) {
     LOG(ERROR) << "Invalid polynomial of size 0 passed to FindPolynomialRoots";
     return false;