Remove tests for now non-existent method CI_Upload::clean_file_name()

See 7e5597782a589e4171ca08abdd9ce1a185542ff4
diff --git a/tests/codeigniter/libraries/Upload_test.php b/tests/codeigniter/libraries/Upload_test.php
index 1bd8f14..4d9e4a4 100644
--- a/tests/codeigniter/libraries/Upload_test.php
+++ b/tests/codeigniter/libraries/Upload_test.php
@@ -208,12 +208,6 @@
 		$this->assertEquals('', $this->upload->get_extension('hello'));
 	}
 
-	function test_clean_file_name()
-	{
-		$this->assertEquals('hello.txt', $this->upload->clean_file_name('hello.txt'));
-		$this->assertEquals('hello.txt', $this->upload->clean_file_name('%253chell>o.txt'));
-	}
-
 	function test_limit_filename_length()
 	{
 		$this->assertEquals('hello.txt', $this->upload->limit_filename_length('hello.txt', 10));