Remove Oculus support from code

Moved to custom example, now raylib only supports simulated VR
rendering.
Oculus code was too device dependant... waiting for OpenXR.

src/core.c

@@ -755,11 +755,8 @@ void End2dMode(void)
 void Begin3dMode(Camera camera)
 {
     rlglDraw();                         // Draw Buffers (Only OpenGL 3+ and ES2)
-
-    if (IsVrDeviceReady() || IsVrSimulator()) BeginVrDrawing();
-
+    
     rlMatrixMode(RL_PROJECTION);        // Switch to projection matrix
-
     rlPushMatrix();                     // Save previous matrix, which contains the settings for the 2d ortho projection
     rlLoadIdentity();                   // Reset current matrix (PROJECTION)
 
@@ -786,8 +783,6 @@ void End3dMode(void)
 {
     rlglDraw();                         // Process internal buffers (update + draw)
 
-    if (IsVrDeviceReady() || IsVrSimulator()) EndVrDrawing();
-
     rlMatrixMode(RL_PROJECTION);        // Switch to projection matrix
     rlPopMatrix();                      // Restore previous matrix (PROJECTION) from matrix stack