Order of Modifiers Amended

When unsigned() was added to a migration with an integer() or bigInteger(), the
order of modifiers would result in a query like:

```sql
`field` int primary key unsigned not null
```

This is invalid SQL and therefore caused errors on the migrations.

Issue reported, with steps to replicate, here:

#37781

src/Illuminate/Database/Schema/Grammars/MySqlGrammar.php

@@ -15,7 +15,7 @@ class MySqlGrammar extends Grammar
      * @var string[]
      */
     protected $modifiers = [
-        'Primary', 'Unsigned', 'Charset', 'Collate', 'VirtualAs', 'StoredAs', 'Nullable',
+        'Unsigned', 'Primary', 'Charset', 'Collate', 'VirtualAs', 'StoredAs', 'Nullable',
         'Srid', 'Default', 'Increment', 'Comment', 'After', 'First',
     ];