Fix minor typo in method descrption

Should fix src/S3fsFileService.php at the same time.

And might as well fix all references to 'the the' as it appears to have slipped into the code in a few places.

tests/src/Functional/S3fsTest.php:    $this->assertNotFalse($s3_file2, "Copied the the first test file to $test_uri2.");
tests/src/Functional/S3fsTest.php:    $this->assertNotFalse($img_file, "Copied the the test image to $img_uri1.");
tests/src/Functional/S3fsImageStyleControllerLockdownTest.php:    $this->assertNotFalse($img_file, "Copied the the test image to $img_uri1.");