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

Partially revert commit 5f2df88b63e50d23914e97ec778861a52abdeaad:
add "#undef Yield" to .c files after including Python-ast.h.

Fix the warning:

    winbase.h(102): warning C4005: 'Yield': macro redefinition
diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
index 14550fd..f0d342a 100644
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -3,6 +3,7 @@
 #include "Python.h"
 #include <ctype.h>
 #include "ast.h"
+#undef Yield   /* undefine macro conflicting with <winbase.h> */
 #include "pycore_pystate.h"
 
 _Py_IDENTIFIER(__builtins__);
diff --git a/Python/import.c b/Python/import.c
index f7c37aa..15637c6 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -3,6 +3,7 @@
 #include "Python.h"
 
 #include "Python-ast.h"
+#undef Yield   /* undefine macro conflicting with <winbase.h> */
 #include "pycore_pyhash.h"
 #include "pycore_pylifecycle.h"
 #include "pycore_pymem.h"
diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
index 58e1647..af3d5ef 100644
--- a/Python/pylifecycle.c
+++ b/Python/pylifecycle.c
@@ -3,6 +3,7 @@
 #include "Python.h"
 
 #include "Python-ast.h"
+#undef Yield   /* undefine macro conflicting with <winbase.h> */
 #include "pycore_context.h"
 #include "pycore_hamt.h"
 #include "pycore_pathconfig.h"
diff --git a/Python/pythonrun.c b/Python/pythonrun.c
index 1bf822c..2d5dc88 100644
--- a/Python/pythonrun.c
+++ b/Python/pythonrun.c
@@ -11,6 +11,7 @@
 #include "Python.h"
 
 #include "Python-ast.h"
+#undef Yield   /* undefine macro conflicting with <winbase.h> */
 #include "pycore_pystate.h"
 #include "grammar.h"
 #include "node.h"
diff --git a/Python/symtable.c b/Python/symtable.c
index 96f7bcd..677b604 100644
--- a/Python/symtable.c
+++ b/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 */