message: Fix bazel build with -DTF_LITE_STATIC_MEMORY.
  Tested that the following command passes:
  ```
  bazel test tensorflow/lite/micro/...  --test_tag_filters=-no_oss --build_tag_filters=-no_oss --copt=-DTF_LITE_STATIC_MEMORY
  ```
  Addresses
diff: @@ -36,6 +36,8 @@ TfLiteRegistration* Register_DETECTION_POSTPROCESS();
  template <unsigned int tOpCount>
  class MicroMutableOpResolver : public MicroOpResolver {
  public:
  + TF_LITE_REMOVE_VIRTUAL_DELETE
  +
  explicit MicroMutableOpResolver(ErrorReporter* error_reporter = nullptr)
  : error_reporter_(error_reporter) {}
  @@ -421,8 +423,6 @@ class MicroMutableOpResolver : public MicroOpResolver {
  unsigned int GetRegistrationLength() { return registrations_len_; }
  private:
  - TF_LITE_REMOVE_VIRTUAL_DELETE
  -
  TfLiteStatus AddBuiltin(tflite::BuiltinOperator op,
  const TfLiteRegistration& registration,
  MicroOpResolver::BuiltinParseFunction parser) {
  