### Godot version

v4.2.dev4.official [549fcce5f]

### System information

Ubuntu 20.04 LTS

### Issue description

See title.

### Steps to reproduce

1. Create a new project
2. Create a csv file that includes the following
```
key,ar
key,placeholder
```
3. Add the generated `.translation` file to Project -> Project Settings... -> Localization
4. In Project -> Project Settings... -> Internationalization -> Locale, set `Test` to `ar`
5. Add a `LineEdit` node and type `-=[]{}`
6. Run the project, and notice that the text is on the right side, but the symbols are incorrectly in LTR (`-=[]{}`).  Correct output is `{}[]=-`
7. Back in the editor, add a single Arabic letter (any will do), and notice that `LineEdit` immediately (and correctly) flips the symbols, and the newly-added Arabic letter, to RTL.

**Notes**
- Identical behavior is seen with `TextEdit`.
- The purpose of steps 2-4 are to simulate an Arabic environment when the project is run, despite `OS.get_locale() == "en"` (or your system's current language).

### Minimal reproduction project

[rtlsymbols.zip](https://github.com/godotengine/godot/files/12525509/rtlsymbols.zip)
if (!p_sd->chars_valid) {
		p_sd->chars.clear();
		const UChar *data = p_sd->utf16.get_data();
		UErrorCode err = U_ZERO_ERROR;
		int prev = -1;
		int i = 0;
		Vector<ShapedTextDataAdvanced::Span> &spans = p_sd->spans;
		if (p_sd->parent != RID()) {
			ShapedTextDataAdvanced *parent_sd = shaped_owner.get_or_null(p_sd->parent);
			ERR_FAIL_COND(!parent_sd->valid);
			spans = parent_sd->spans;
		}
		while (i < spans.size()) {
			if (spans[i].start > p_sd->end) {
				
			}
			if (spans[i].end < p_sd->start) {
				i++;
				continue;
			}
			int r_start = MAX(0, spans[i].start - p_sd->start);
			String language = spans[i].language;
			while (i + 1 < spans.size() && language == spans[i + 1].language) {
				i++;
			}
			int r_end = MIN(spans[i].end - p_sd->start, p_sd->text.length());
			UBreakIterator *bi = ubrk_open(UBRK_CHARACTER, (language.is_empty()) ? TranslationServer::get_singleton()->get_tool_locale().ascii().get_data() : language.ascii().get_data(), data + _convert_pos_inv(p_sd, r_start), _convert_pos_inv(p_sd, r_end - r_start), &err);
			if (U_SUCCESS(err)) {
				while (ubrk_next(bi) != UBRK_DONE) {
					int pos = _convert_pos(p_sd, ubrk_current(bi)) + r_start + p_sd->start;