Update matchAll to include first only matching group (laravel#9683)

* Update matchAll to include first only matching group

* Update strings.md

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Co-authored-by: Taylor Otwell <taylor@laravel.com>

Author: django23

strings.md

@@ -2031,7 +2031,7 @@ The `matchAll` method will return a collection containing the portions of a stri
 
     // collect(['bar', 'bar'])
 
-If you specify a matching group within the expression, Laravel will return a collection of that group's matches:
+If you specify a matching group within the expression, Laravel will return a collection of the first matching group's matches:
 
     use Illuminate\Support\Str;