Fix parameters in bpy.props.StringProperty Python API docs

There is a parameter typo in Python API document about bpy.props.StringProperty.
This patch fixes this.

Also this patch should apply to 2.90 branch as well.

Reviewed By: Grische, mont29

Differential Revision: https://developer.blender.org/D8430

source/blender/python/intern/bpy_props.c

@@ -2961,7 +2961,7 @@ PyDoc_STRVAR(BPy_StringProperty_doc,
              "default=\"\", "
              "maxlen=0, "
              "options={'ANIMATABLE'}, "
-             "options=set(), "
+             "override=set(), "
              "tags=set(), "
              "subtype='NONE', "
              "update=None, "