bug #5663 Use "disabled" color on select too (lyrixx)

This PR was merged into the 4.x branch.

Discussion
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Use "disabled" color on select too

Before
![image](https://user-images.githubusercontent.com/408368/223409507-48b349cb-bf07-42df-b7ac-872947a2f216.png)

After

![image](https://user-images.githubusercontent.com/408368/223409572-1c02df7d-ed8b-4d62-883c-9f116fced11f.png)

---

refs: https://github.com/symfony/symfony/blob/6.3/src/Symfony/Bridge/Twig/Resources/views/Form/bootstrap_5_layout.html.twig#L257

Commits
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63051aa Use "disabled" color on select too

assets/css/easyadmin-theme/forms.scss

@@ -105,7 +105,9 @@ label.form-check-label {
 }
 
 .form-widget .form-control:disabled,
-.form-widget .form-control[readonly] {
+.form-widget .form-control[readonly],
+.form-widget .form-select:disabled,
+.form-widget .form-select[readonly] {
     background-color: var(--form-control-disabled-bg);
     color: var(--form-control-disabled-color);
 }