Minor change in documentation related to open field indexing (including a non-terminal name change in the documented grammar).
Minor change in documentation related to open field indexing
(including a non-terminal name change in the documented grammar).

Change-Id: Iaf647dc48c3f4d5b9bcb09ad198b815959cde2d5
Reviewed-on: https://asterix-gerrit.ics.uci.edu/417
Reviewed-by: Ian Maxon <75f98fe183e5455573e3e67a0344be46e7dea75a@apache.org>
Tested-by: Jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@fulliautomatix.ics.uci.edu>

kisskys/incubator-asterixdb,ecarm002/incubator-asterixdb,ecarm002/incubator-asterixdb,apache/incubator-asterixdb,waans11/incubator-asterixdb,ecarm002/incubator-asterixdb,heriram/incubator-asterixdb,ty1er/incubator-asterixdb,waans11/incubator-asterixdb,waans11/incubator-asterixdb,apache/incubator-asterixdb,ty1er/incubator-asterixdb,kisskys/incubator-asterixdb,apache/incubator-asterixdb,ecarm002/incubator-asterixdb,heriram/incubator-asterixdb,apache/incubator-asterixdb,kisskys/incubator-asterixdb,heriram/incubator-asterixdb,apache/incubator-asterixdb,waans11/incubator-asterixdb,heriram/incubator-asterixdb,ecarm002/incubator-asterixdb,waans11/incubator-asterixdb,ty1er/incubator-asterixdb,ty1er/incubator-asterixdb,ty1er/incubator-asterixdb,ecarm002/incubator-asterixdb,heriram/incubator-asterixdb,kisskys/incubator-asterixdb,ty1er/incubator-asterixdb,waans11/incubator-asterixdb,heriram/incubator-asterixdb,heriram/incubator-asterixdb,apache/incubator-asterixdb,apache/incubator-asterixdb,kisskys/incubator-asterixdb,waans11/incubator-asterixdb,ecarm002/incubator-asterixdb,kisskys/incubator-asterixdb,kisskys/incubator-asterixdb