Merge #5761

5761: Replace `POPUP_PURE` with generic `PopupMessage` r=def- a=Robyt3

Minor refactoring, as the popup just shows generic text with an Ok-button.

## Checklist

- [X] Tested the change ingame
- [ ] Provided screenshots if it is a visual change
- [ ] Tested in combination with possibly related configuration options
- [ ] Written a unit test (especially base/) or added coverage to integration test
- [ ] Considered possible null pointers and out of bounds array indexing
- [ ] Changed no physics that affect existing maps
- [ ] Tested the change with [ASan+UBSan or valgrind's memcheck](https://github.com/ddnet/ddnet/#using-addresssanitizer--undefinedbehavioursanitizer-or-valgrinds-memcheck) (optional)


Co-authored-by: Robert Müller <robytemueller@gmail.com>

src/game/client/components/menus.cpp

@@ -1510,13 +1510,6 @@ int CMenus::Render()
 			}
 			ExtraAlign = 0;
 		}
-		else if(m_Popup == POPUP_PURE)
-		{
-			pTitle = Localize("Disconnected");
-			pExtraText = Localize("The server is running a non-standard tuning on a pure game type.");
-			pButtonText = Localize("Ok");
-			ExtraAlign = -1;
-		}
 		else if(m_Popup == POPUP_DELETE_DEMO)
 		{
 			pTitle = Localize("Delete demo");
@@ -2528,7 +2521,7 @@ void CMenus::OnRender()
 	{
 		Client()->Disconnect();
 		SetActive(true);
-		m_Popup = POPUP_PURE;
+		PopupMessage(Localize("Disconnected"), Localize("The server is running a non-standard tuning on a pure game type."), Localize("Ok"));
 	}
 
 	if(!IsActive())

src/game/client/components/menus.h

@@ -684,7 +684,6 @@ public:
 		POPUP_CONNECTING,
 		POPUP_MESSAGE,
 		POPUP_DISCONNECTED,
-		POPUP_PURE,
 		POPUP_LANGUAGE,
 		POPUP_COUNTRY,
 		POPUP_DELETE_DEMO,