Keep end of ScriptEditor tab history when closing tab

[TheDying0fLight]

When closing a tab while not at the end of the history all entries after the current idx are deleted. This PRs goal is to ensure that the rest of the history is kept.

Note: There currently is an issue with the history when working with script files (see #113619). So I only used files from the internal documentation for testing this

Example

------- history -----
0 :  AABB
1 :  float <--- this is closed
2 :  ClassDB
3 :  bool
curr idx:  1

Closing 1: float

Without PR

------- history -----
0 :  AABB
curr idx:  0

With PR

------- history -----
0 :  AABB
1 :  ClassDB
2 :  bool
curr idx:  0