gh-132174: Fix function name in error message of _interpreters.run_string (#132175)

Co-authored-by: Brian Schubert <brianm.schubert@gmail.com>

Misc/NEWS.d/next/Library/2025-04-06-23-16-08.gh-issue-132174.dN4b-X.rst

@@ -0,0 +1 @@
+Fix function name in error message of ``_interpreters.run_string``.

Modules/_interpretersmodule.c

@@ -1112,7 +1112,7 @@ interp_run_string(PyObject *self, PyObject *args, PyObject *kwds)
         return NULL;
     }
 
-    script = (PyObject *)convert_script_arg(script, MODULE_NAME_STR ".exec",
+    script = (PyObject *)convert_script_arg(script, MODULE_NAME_STR ".run_string",
                                             "argument 2", "a string");
     if (script == NULL) {
         return NULL;