message: Remove unneeded using statements in coefficient.hpp
diff: @@ -1319,7 +1319,6 @@ public:
  virtual void Eval(DenseSymmetricMatrix &K, ElementTransformation &T,
  const IntegrationPoint &ip) = 0;
  - using MatrixCoefficient::Eval;
  /** @brief Evaluate the matrix coefficient in the element described by @a T
  at the point @a ip, storing the result as a dense matrix @a K. */
  /** This function allows the use of SymmetricMatrixCoefficient in situations
  @@ -1400,7 +1399,6 @@ public:
  /// Set the time for internally stored coefficients
  void SetTime(double t);
  - using MatrixCoefficient::Eval;
  using SymmetricMatrixCoefficient::Eval;
  /// Evaluate the matrix coefficient at @a ip.
  virtual void Eval(DenseSymmetricMatrix &K, ElementTransformation &T,
  