Login Language Dropdown: Remove Flag Icon (#3037)

# Description of Changes

Please provide a summary of the changes, including:

Removed the flag icon image element from the language dropdown button in
the login template (`login.html`).

Closes #(issue_number)

---

## Checklist

### 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)
- [ ] 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)
- [ ] 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.

src/main/resources/templates/login.html

@@ -138,7 +138,7 @@
         <div class="mt-3"> <!-- Added a margin-top for spacing -->
           <div class="dropdown text-center">
             <button class="btn btn-secondary dropdown-toggle" type="button" id="languageDropdown" data-bs-toggle="dropdown" aria-expanded="false">
-              <img th:src="@{'/images/flags/gb.svg'}" alt="icon" width="20" height="15"> English (GB)
+              English (GB)
               <!-- Default language placeholder -->
             </button>
             <div class="dropdown-menu" aria-labelledby="languageDropdown">