Remove \WC_Customer::get_hook_prefix method

This method is now redundant since the `$object_type` property is set for the class. This means the parent method will now return the exact same value.

includes/class-wc-customer.php

@@ -126,16 +126,6 @@ class WC_Customer extends WC_Legacy_Customer {
 		}
 	}
 
-	/**
-	 * Prefix for action and filter hooks on data.
-	 *
-	 * @since  3.0.0
-	 * @return string
-	 */
-	protected function get_hook_prefix() {
-		return 'woocommerce_customer_get_';
-	}
-
 	/**
 	 * Delete a customer and reassign posts..
 	 *