removes version guard (#3173)

We currently use a version guard to adapt to a change in the number of parameters supplied to osg::TriangleFunctor's operator() template functor. The differing parameter is unused in our code. Crucially, operator() is not an override, so we can just add a default value for the differing parameter. Such a default allows us to apply identical code to both versions of the library without regressing functionality.

components/resource/bulletshapemanager.cpp

@@ -4,7 +4,6 @@
 #include <osg/TriangleFunctor>
 #include <osg/Transform>
 #include <osg/Drawable>
-#include <osg/Version>
 
 #include <BulletCollision/CollisionShapes/btTriangleMesh.h>
 
@@ -45,11 +44,7 @@ struct GetTriangleFunctor
         return btVector3(vec.x(), vec.y(), vec.z());
     }
 
-#if OSG_MIN_VERSION_REQUIRED(3,5,6)
-    void inline operator()( const osg::Vec3& v1, const osg::Vec3& v2, const osg::Vec3& v3 )
-#else
-    void inline operator()( const osg::Vec3& v1, const osg::Vec3& v2, const osg::Vec3& v3, bool _temp )
-#endif
+    void inline operator()( const osg::Vec3& v1, const osg::Vec3& v2, const osg::Vec3& v3, bool _temp=false ) // Note: unused temp argument left here for OSG versions less than 3.5.6 
     {
         if (mTriMesh)
             mTriMesh->addTriangle( toBullet(mMatrix.preMult(v1)), toBullet(mMatrix.preMult(v2)), toBullet(mMatrix.preMult(v3)));