Rephrase !PyErr_Occurred() comment: may=>can

Issue #29259.
diff --git a/Objects/abstract.c b/Objects/abstract.c
index 1132b84..7b1f196 100644
--- a/Objects/abstract.c
+++ b/Objects/abstract.c
@@ -2233,7 +2233,7 @@
     PyObject *result;
 
     /* PyObject_Call() must not be called with an exception set,
-       because it may clear it (directly or indirectly) and so the
+       because it can clear it (directly or indirectly) and so the
        caller loses its exception */
     assert(!PyErr_Occurred());
     assert(PyTuple_Check(args));
@@ -2309,7 +2309,7 @@
     PyObject *result = NULL;
 
     /* _PyObject_FastCallDict() must not be called with an exception set,
-       because it may clear it (directly or indirectly) and so the
+       because it can clear it (directly or indirectly) and so the
        caller loses its exception */
     assert(!PyErr_Occurred());