[10.x] Fix test name for stringable position (laravel#48480)

Co-authored-by: Shawn Lindstrom <[email protected]>

tests/Support/SupportStringableTest.php

@@ -1024,7 +1024,7 @@ public function testSubstrCount()
         $this->assertSame(1, $this->stringable('laravelPHPFramework')->substrCount('a', -10, -3));
     }
 
-    public function testSubstrPos()
+    public function testPosition()
     {
         $this->assertSame(7, $this->stringable('Hello, World!')->position('W'));
         $this->assertSame(10, $this->stringable('This is a test string.')->position('test'));