CSV translation file is not reimported when changed

### Tested versions

- Reproducible in 4.6-stable

### System information

Windows 10

### Issue description

It seems csv translation file is not reimported when changed. Thus changes are not reflected in game when run in editor. A restart or manual reimport resolve the problem.

### Steps to reproduce

Setup i18n.csv translation file in your project with i18n.en.translation and i18n.fr.translation
Use it in code with tr("YOUR_KEY").
Change or add a translations.
Run game.
Changes are not taken in account.
(you should restart or manually reimport csv)

In MRP, test.gd is editor script made to show problem if you change translation by adding a character 2 at end and saving ; note that tr() is not working in editor script for whatever reason (bug ? feature ? who knows).
You can do the same by running game and observing console.

### Minimal reproduction project (MRP)

[translation-change-not-detected.zip](https://github.com/user-attachments/files/24897109/translation-change-not-detected.zip)

Start by running the linked minimal reproduction project and inspect test.gd, then observe how changes to i18n.csv affect i18n.en.translation and i18n.fr.translation in the editor and during game execution. Trace the CSV translation import path to determine why saving the file does not trigger reimport; done means changes are reflected without restarting or manually reimporting.

Written by the indexing model from the issue text.