README: fix typo in guarantees

Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>

Author: cyphar

README.md

@@ -29,8 +29,8 @@ func SecureJoin(root, unsafePath string) (string, error)
 This library **guarantees** the following:
 
 * If no error is set, the resulting string **must** be a child path of
-  `SecureJoin` and will not contain any symlink path components (they will all
-  be expanded).
+  `root` and will not contain any symlink path components (they will all be
+  expanded).
 
 * When expanding symlinks, all symlink path components **must** be resolved
   relative to the provided root. In particular, this can be considered a