bpo-35177, Python-ast.h: Fix "Yield" compiler warning (GH-10664)

Partially revert commit 5f2df88b63:
add "#undef Yield" to .c files after including Python-ast.h.

Fix the warning:

    winbase.h(102): warning C4005: 'Yield': macro redefinition

Python/symtable.c

@@ -1,6 +1,7 @@
 #include "Python.h"
 #include "pycore_pystate.h"
 #include "symtable.h"
+#undef Yield   /* undefine macro conflicting with <winbase.h> */
 #include "structmember.h"
 
 /* error strings used for warnings */