bpo-31567: add or fix decorator markup in docs (#3959)

diff --git a/Doc/library/test.rst b/Doc/library/test.rst
index 33978e3..01ba1ec 100644
--- a/Doc/library/test.rst
+++ b/Doc/library/test.rst
@@ -440,7 +440,7 @@
    otherwise.
 
 
-.. decorator:: skip_unless_symlink()
+.. decorator:: skip_unless_symlink
 
    A decorator for running tests that require support for symbolic links.