fix: added missing language string en_GB, sl_SI (#2908)

# Description of Changes

Please provide a summary of the changes, including:

- added missing language string: redact.applyChanges=Apply Changes

### General

- [x] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [x] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md)
(if applicable)
- [x] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/HowToAddNewLanguage.md)
(if applicable)
- [x] I have performed a self-review of my own code
- [x] My changes generate no new warnings

### Documentation

- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [x] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### UI Changes (if applicable)

- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [ ] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md#6-testing)
for more details.

Co-authored-by: blaz.carli <blaz.carli@arctur.si>

src/main/resources/messages_en_GB.properties

@@ -623,6 +623,7 @@ redact.showAttatchments=Show Attachments
 redact.showLayers=Show Layers (double-click to reset all layers to the default state)
 redact.colourPicker=Colour Picker
 redact.findCurrentOutlineItem=Find current outline item
+redact.applyChanges=Apply Changes
 
 #showJS
 showJS.title=Show Javascript

src/main/resources/messages_sl_SI.properties

@@ -623,6 +623,7 @@ redact.showAttatchments=Prikaži priloge
 redact.showLayers=Prikaži plasti (dvokliknite za ponastavitev vseh plasti na privzeto stanje)
 redact.colourPicker=Izbirnik barv
 redact.findCurrentOutlineItem=Poišči trenutno postavko orisa
+redact.applyChanges=Uporabi spremembe
 
 #showJS
 showJS.title=Prikaži Javascript