STYLE: Replace NumericTraits<unsigned int>::ZeroValue() with 0U

Style improvement within the default-constructor of
`GradientDescentLineSearchOptimizer`, suggested by Mihail Isakov.

Modules/Numerics/Optimizersv4/include/itkGradientDescentLineSearchOptimizerv4.hxx

@@ -27,7 +27,7 @@ GradientDescentLineSearchOptimizerv4Template<
   TInternalComputationValueType>::GradientDescentLineSearchOptimizerv4Template()
 {
   this->m_MaximumLineSearchIterations = 20;
-  this->m_LineSearchIterations = NumericTraits<unsigned int>::ZeroValue();
+  this->m_LineSearchIterations = 0U;
   this->m_LowerLimit = itk::NumericTraits<TInternalComputationValueType>::ZeroValue();
   this->m_UpperLimit = 5.0;
   this->m_Phi = 1.618034;