Cleanup: remove unnecessary PyErr_Fetch/Restore use in bpy_rna

srna_from_self had logic to replace the exception unless there was
already an exception set. This logic isn't needed, except in some
disabled code which has been updated. If srna_from_self ran with an
exception set it would leak memory in Python 3.12.

source/blender/python/intern/bpy_rna.cc

@@ -4513,15 +4513,20 @@ static PyObject *pyrna_struct_meta_idprop_getattro(PyObject *cls, PyObject *attr
  * this is faking internal behavior in a way that's too tricky to maintain well. */
 #  if 0
   if ((ret == nullptr) /* || BPy_PropDeferred_CheckTypeExact(ret) */) {
+    PyErr_Clear(); /* Clear error from tp_getattro. */
     StructRNA *srna = srna_from_self(cls, "StructRNA.__getattr__");
     if (srna) {
       PropertyRNA *prop = RNA_struct_type_find_property_no_base(srna, PyUnicode_AsUTF8(attr));
       if (prop) {
-        PyErr_Clear(); /* Clear error from tp_getattro. */
         PointerRNA tptr = RNA_pointer_create(nullptr, &RNA_Property, prop);
         ret = pyrna_struct_CreatePyObject(&tptr);
       }
     }
+    if (ret == nullptr) {
+      PyErr_Format(PyExc_AttributeError,
+                   "StructRNA.__getattr__: attribute \"%.200s\" not found",
+                   PyUnicode_AsUTF8(attr));
+    }
   }
 #  endif
 
@@ -7949,7 +7954,6 @@ int pyrna_struct_as_ptr_or_null_parse(PyObject *o, void *p)
 
 StructRNA *srna_from_self(PyObject *self, const char *error_prefix)
 {
-
   if (self == nullptr) {
     return nullptr;
   }
@@ -7961,19 +7965,8 @@ StructRNA *srna_from_self(PyObject *self, const char *error_prefix)
   }
 
   /* These cases above not errors, they just mean the type was not compatible
-   * After this any errors will be raised in the script */
-
-  PyObject *error_type, *error_value, *error_traceback;
-  StructRNA *srna;
-
-  PyErr_Fetch(&error_type, &error_value, &error_traceback);
-  srna = pyrna_struct_as_srna(self, false, error_prefix);
-
-  if (!PyErr_Occurred()) {
-    PyErr_Restore(error_type, error_value, error_traceback);
-  }
-
-  return srna;
+   * After this any errors will be raised in the script. */
+  return pyrna_struct_as_srna(self, false, error_prefix);
 }
 
 static int deferred_register_prop(StructRNA *srna, PyObject *key, PyObject *item)