[DeadCode] Skip array dim fetch assign in RemoveDefaultValueFromAssignedPropertyRector

[TomasVotruba]

Fixes rectorphp/rector#9826

$this->default['tplset'] = 'dotty'; was treated as a full property assign, because PropertyAssignMatcher intentionally also matches $this->prop[...] = (useful for type inference). A partial array assign does not overwrite the property, so the default value is still required.

Skip the property when it is assigned via array dim fetch, incl. nested dims.

 class ModuleDefine
 {
    private array $default = [
        'name' => 'some name',
        'tplset' => null,
    ];

     public function __construct()
     {
         $this->default['tplset'] = 'dotty';
     }
 }

Before this PR the default value was removed, leaving private array $default; and an uninitialized property → Error: Typed property must not be accessed before initialization.