TabItem: revert support for SetNextItemOpen(true) at it creates too much ambiguity with p_open/close button vs Selected state. (#5262)

Revert a small part of 4b97296.

docs/CHANGELOG.txt

@@ -105,7 +105,7 @@ Other Changes:
   merging drawcall of the last column didn't always work (regression since 1.87). (#4843, #4844) [@rokups]
 - Inputs: Fixed IsMouseClicked() repeat mode rate being half of keyboard repeat rate.
 - ColorEdit: Fixed text baseline alignment after a SameLine() after a ColorEdit() with visible label.
-- TabBar: TabItem() now reacts to SetNextItemWidth() and SetNextItemOpen(true). (#5262)
+- TabBar: TabItem() now reacts to SetNextItemWidth(). (#5262)
 - TabBar: Tweak shrinking policy so that while resizing tabs that don't need shrinking keep their
   initial width more precisely (without the occasional +1 worth of width).
 - Menus: Adjusted BeginMenu() closing logic so hovering void or non-MenuItem() in parent window

imgui_widgets.cpp

@@ -8105,11 +8105,6 @@ bool    ImGui::TabItemEx(ImGuiTabBar* tab_bar, const char* label, bool* p_open,
                 tab_bar->NextSelectedTabId = id;  // New tabs gets activated
         if ((flags & ImGuiTabItemFlags_SetSelected) && (tab_bar->SelectedTabId != id)) // _SetSelected can only be passed on explicit tab bar
             tab_bar->NextSelectedTabId = id;
-        if (g.NextItemData.Flags & ImGuiNextItemDataFlags_HasOpen)
-        {
-            IM_ASSERT(g.NextItemData.OpenVal == true && g.NextItemData.OpenCond == ImGuiCond_Always); // SetNextItemOpen(true, ImGuiCond_Always) is supported but other combinations are not.
-            tab_bar->NextSelectedTabId = id;
-        }
     }
 
     // Lock visibility