[deprecation] Deprecate AddReturnDocblockForDimFetchArrayFromAssignsRector

[TomasVotruba]

The rule guesses an array shape from conditional assigns inside a method body, then writes it as a @return docblock.

That guess only holds if the method body is the whole story. Any later assign, a loop, a dynamic key or a caller-side mutation widens the real type, and the docblock is then too narrow - a silently wrong annotation that PHPStan trusts.

 final class SomeClass
 {
+    /**
+     * @return array<string, string>
+     */
     public function toArray(): array
     {
         $items = [];

         if (mt_rand(0, 1)) {
             $items['key'] = 'value';
         }

         return $items;
     }
 }

The narrow array<string, string> is only correct by accident here; one $items[] = new Item() elsewhere makes it a lie.

Add the docblock manually, or write a custom rule with project-specific knowledge.

Changes:

• rule implements DeprecatedInterface and throws on refactor()
• removed from the TypeDeclarationDocblocksLevel set
• test case + fixtures removed