pointer constraints: don't warp pointer position on release

this was annoying for nuklear properties/ui slider elements that grab
the pointer via GLFW_CURSOR_DISABLE to allow more range and finer control.
upon mouse release, the pointer is reset to the middle of the window
without this patch, making long mouse movements necessary to go back
to the original position for readjustments. fwiw the new behaviour
is consistent with x11 and weston.

src/protocols/PointerConstraints.cpp

@@ -188,7 +188,7 @@ Vector2D CPointerConstraint::logicPositionHint() {
     const auto SURFBOX       = pHLSurface->getSurfaceBoxGlobal();
     const auto CONSTRAINTPOS = SURFBOX.has_value() ? SURFBOX->pos() : Vector2D{};
 
-    return hintSet ? CONSTRAINTPOS + positionHint : (locked ? CONSTRAINTPOS + SURFBOX->size() / 2.f : cursorPosOnActivate);
+    return hintSet ? CONSTRAINTPOS + positionHint : cursorPosOnActivate;
 }
 
 CPointerConstraintsProtocol::CPointerConstraintsProtocol(const wl_interface* iface, const int& ver, const std::string& name) : IWaylandProtocol(iface, ver, name) {