bug #15150 [Translation] Azerbaijani language pluralization rule is wrong (shehi)

This PR was submitted for the 2.8 branch but it was merged into the 2.3 branch instead (closes #15150).

Discussion
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[Translation] Azerbaijani language pluralization rule is wrong

In AZ, as in TR, pluralization is always 0:

0 kitab (zero books)
1 kitab (1 book)
3 kitab (3 books)
104 kitab (104 books)

Apparently ZF ruleset was wrong in the first place :)

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #15152
| License       | MIT
| Doc PR        | -

Commits
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efd927a Azerbaijani language pluralization rule

src/Symfony/Component/Translation/PluralizationRules.php

@@ -56,6 +56,7 @@ class PluralizationRules
          * Copyright (c) 2005-2010 Zend Technologies USA Inc. (http://www.zend.com)
          */
         switch ($locale) {
+            case 'az':
             case 'bo':
             case 'dz':
             case 'id':
@@ -74,7 +75,6 @@ class PluralizationRules
                 break;
 
             case 'af':
-            case 'az':
             case 'bn':
             case 'bg':
             case 'ca':