ScrollToRectEx: Fix bug where scrolling horizontally to an always-centered element that is not visible but could be would take the item's Y coordinate into account.

Neither behavior were used in the codebase for this axis.
Amend 27c58c39 (#5902, #2812, #4242, #2900)
Signed-off-by: Neil Bickford <nbickford@nvidia.com>

imgui.cpp

@@ -9666,7 +9666,7 @@ ImVec2 ImGui::ScrollToRectEx(ImGuiWindow* window, const ImRect& item_rect, ImGui
     else if (((flags & ImGuiScrollFlags_KeepVisibleCenterX) && !fully_visible_x) || (flags & ImGuiScrollFlags_AlwaysCenterX))
     {
         if (can_be_fully_visible_x)
-            SetScrollFromPosX(window, ImFloor((item_rect.Min.x + item_rect.Max.y) * 0.5f) - window->Pos.x, 0.5f);
+            SetScrollFromPosX(window, ImFloor((item_rect.Min.x + item_rect.Max.x) * 0.5f) - window->Pos.x, 0.5f);
         else
             SetScrollFromPosX(window, item_rect.Min.x - window->Pos.x, 0.0f);
     }