minor #43482 [Validator] Improve German translation (derrabus)

This PR was merged into the 4.4 branch.

Discussion
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[Validator] Improve German translation

| Q             | A
| ------------- | ---
| Branch?       | 4.4
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Tickets       | Improves #43480
| License       | MIT
| Doc PR        | N/A

I was too late with my review apparently. 🙈

We usually translate "valid" as "gültig". We should do the same here.

Commits
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fa29a58 [Validator] Improve German translation

src/Symfony/Component/Validator/Resources/translations/validators.de.xlf

@@ -392,7 +392,7 @@
             </trans-unit>
             <trans-unit id="101">
                 <source>This value is not a valid CSS color.</source>
-                <target>Dieser Wert ist keine valide CSS Farbe.</target>
+                <target>Dieser Wert ist keine gültige CSS-Farbe.</target>
             </trans-unit>
         </body>
     </file>