bpo-39943: Remove unnecessary casts in import.c that remove constness (GH-19209)

diff --git a/Python/import.c b/Python/import.c
index 5d500df..2e43456 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -1763,14 +1763,14 @@
     }
 
     if (PyDTrace_IMPORT_FIND_LOAD_START_ENABLED())
-        PyDTrace_IMPORT_FIND_LOAD_START((char *)PyUnicode_AsUTF8(abs_name));
+        PyDTrace_IMPORT_FIND_LOAD_START(PyUnicode_AsUTF8(abs_name));
 
     mod = _PyObject_CallMethodIdObjArgs(interp->importlib,
                                         &PyId__find_and_load, abs_name,
                                         interp->import_func, NULL);
 
     if (PyDTrace_IMPORT_FIND_LOAD_DONE_ENABLED())
-        PyDTrace_IMPORT_FIND_LOAD_DONE((char *)PyUnicode_AsUTF8(abs_name),
+        PyDTrace_IMPORT_FIND_LOAD_DONE(PyUnicode_AsUTF8(abs_name),
                                        mod != NULL);
 
     if (import_time) {