[5.2] Update Str::plural() to use intval() (laravel#14502)

* Update Str::plural() to use intval()

A lot of the time when you use str_plural() you get the $count value from a form request which returns the number as a string and therefore this plural won't work as expected. This small change should make sure the $count is in integer format.

Thanks to @barryvdh for suggesting to do this change deeper in the code.

* Changed to type casting

Using `(int) $count` instead of `intval($count)` as requested.

src/Illuminate/Support/Pluralizer.php

@@ -50,7 +50,7 @@ class Pluralizer
      */
     public static function plural($value, $count = 2)
     {
-        if ($count === 1 || static::uncountable($value)) {
+        if ((int) $count === 1 || static::uncountable($value)) {
             return $value;
         }