Fix typos in mmap() error messages (GH-6173)

(cherry picked from commit 9308dea3)
Co-authored-by: Zackery Spytz <zspytz@gmail.com>

Modules/mmapmodule.c

@@ -1114,7 +1114,7 @@ new_mmap_object(PyTypeObject *type, PyObject *args, PyObject *kwdict)
         return NULL;
     if (map_size < 0) {
         PyErr_SetString(PyExc_OverflowError,
-                        "memory mapped length must be postiive");
+                        "memory mapped length must be positive");
         return NULL;
     }
     if (offset < 0) {
@@ -1300,7 +1300,7 @@ new_mmap_object(PyTypeObject *type, PyObject *args, PyObject *kwdict)
 
     if (map_size < 0) {
         PyErr_SetString(PyExc_OverflowError,
-                        "memory mapped length must be postiive");
+                        "memory mapped length must be positive");
         return NULL;
     }
     if (offset < 0) {