minor #43475 [Validator] Update validators.sl.xlf (juricav)

This PR was merged into the 4.4 branch.

Discussion
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[Validator] Update validators.sl.xlf

| Q             | A
| ------------- | ---
| Branch?       | 4.4
| Bug fix?      | no
| New feature?  | no <!-- please update src/**/CHANGELOG.md files -->
| Deprecations? | no <!-- please update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Tickets       | Fix #43456 <!-- prefix each issue number with "Fix #", no need to create an issue if none exist, explain below instead -->
| License       | MIT
| Doc PR        | symfony/symfony-docs#... <!-- required for new features -->

Add missing validation.

Commits
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7cb4296a27 Update validators.sl.xlf

Author: fabpot

Resources/translations/validators.sl.xlf

@@ -390,6 +390,10 @@
                 <source>This value should be a valid expression.</source>
                 <target>Ta vrednost bi morala biti veljaven izraz.</target>
             </trans-unit>
+            <trans-unit id="101">
+                <source>This value is not a valid CSS color.</source>
+                <target>Ta vrednost ni veljavna barva CSS.</target>
+            </trans-unit>
         </body>
     </file>
 </xliff>