Revert "Fix T78823: Slash in custom property name does not work"

This reverts commit cbae82ba96.

This change introduced the following problems:

- We could no longer reliably duplicate or use an existing
  custom property names.
- We could no longer assume a bone or ID name
  can be used in a custom-property.
- Importers that support custom properties (such as FBX)
  could fail with an exception creating custom properties.

source/blender/python/generic/idprop_py_api.c

@@ -20,8 +20,6 @@
 
 #include <Python.h>
 
-#include <string.h>
-
 #include "MEM_guardedalloc.h"
 
 #include "BLI_utildefines.h"
@@ -372,11 +370,6 @@ static const char *idp_try_read_name(PyObject *name_obj)
                       "the length of IDProperty names is limited to 63 characters");
       return NULL;
     }
-
-    if (strchr(name, '\"') || strchr(name, '\\') || strchr(name, '\'')) {
-      PyErr_SetString(PyExc_KeyError, "IDProperty names cannot include \", \\, or \'");
-      return NULL;
-    }
   }
   else {
     name = "";