Fix .editorconfig for tests/parser/ directory

My IDE (PHPStorm) started messing the files in this directory up
because the rule in .editorconfig doesn't match. The tests directory
is directly in the root where the .editorconfig file also lives.
There is no directory before `tests/` that would satisfy the `**/`
pattern.

Bug: T278066
Change-Id: Ie6d9c71f169a259475e3f3eae2674d6994e2f264

Author: thiemowmde

.editorconfig

@@ -27,5 +27,5 @@ indent_size = 2
 
 # Trailing whitespace is intended in parser test files
 # T278066
-[**/tests/parser/*.txt]
+[tests/parser/*.txt]
 trim_trailing_whitespace = false