Avoid matching the word 'use' outside of imports (#44049)

When using custom stubs the word 'use' is also matched outside of the import statement.
With this change only the lines starting with use are taken into consideration.

Author: cschra

src/Illuminate/Console/GeneratorCommand.php

@@ -355,7 +355,7 @@ protected function replaceClass($stub, $name)
      */
     protected function sortImports($stub)
     {
-        if (preg_match('/(?P<imports>(?:use [^;{]+;$\n?)+)/m', $stub, $match)) {
+        if (preg_match('/(?P<imports>(?:^use [^;{]+;$\n?)+)/m', $stub, $match)) {
             $imports = explode("\n", trim($match['imports']));
 
             sort($imports);