ProductRepository sku cache is destroyed when cacheLimit is reached

Nummeric SKUs are renumbered when array_slice is used to purge parts of the products-by-sku cache array. Per php documentation:
> Note that array_slice() will reorder and reset the numeric array indices by default. 

as `$this->instances` has the SKUs as keys, the resulting shortened array might contain indexes that now point to a wrong product.

Author: heldchen

app/code/Magento/Catalog/Model/ProductRepository.php

@@ -312,7 +312,7 @@ private function cacheProduct($cacheKey, \Magento\Catalog\Api\Data\ProductInterf
         if ($this->cacheLimit && count($this->instances) > $this->cacheLimit) {
             $offset = round($this->cacheLimit / -2);
             $this->instancesById = array_slice($this->instancesById, $offset, null, true);
-            $this->instances = array_slice($this->instances, $offset);
+            $this->instances = array_slice($this->instances, $offset, null, true);
         }
     }