'Replace in Selected Element' button does not work

### Expected behavior

I've been using JMeter's search and replace feature to tweak a bunch of test data, but the problem I'm dealing with now is that the _Replace in selected item_ thing isn't doing what it's supposed to. I thought it should only mess with the selected item, like the button says, leaving the rest alone, but that's not happening.

### Actual behavior

You can spot that the text I'm looking for is in both HTTP requests. But when I hit _Replace in selected item_, the text doesn't change, and it just says _Replaced 0 occurred_.



### Steps to reproduce the problem

Steps:
1. Hit Ctrl + F or Open _Search_ from the toolbar
2. type in "lang": "en" in the _Search_ field.
3. Type in "lang": "ar" in the _Replace by_ field
4. Select any HTTP request under the thread group.
5. Click on _Replace in selected element_

### JMeter Version

5.6.2

### Java Version

java version "20.0.2" 2023-07-18

### OS Version

Microsoft Windows 10.0.19045