Fix reference in the documentation

Author: vstinner

Misc/NEWS.d/3.14.0a1.rst

@@ -4222,7 +4222,7 @@ docstrings are now removed from the optimized AST in optimization level 2.
 .. nonce: A7uxqa
 .. section: Core and Builtins
 
-The ``f_executable`` field in the internal :c:struct:`_PyInterpreterFrame`
+The ``f_executable`` field in the internal :c:struct:`!_PyInterpreterFrame`
 struct now uses a tagged pointer.  Profilers and debuggers that uses this
 field should clear the least significant bit to recover the
 :c:expr:`PyObject*` pointer.