Rename contexthub service.

The Context hub service was not conformant with the other
Android services. As a part of renaming the service and making
it compliant with tradition, the sepolicy must change to reflect
the new name.

Test: GTS tests pass.
Change-Id: I1a666574f45a02e967d0ba97ce597ffb11b2b70b

private/service_contexts

@@ -27,7 +27,7 @@ connectivity_metrics_logger               u:object_r:connectivity_metrics_logger
 connmetrics                               u:object_r:connmetrics_service:s0
 consumer_ir                               u:object_r:consumer_ir_service:s0
 content                                   u:object_r:content_service:s0
-contexthub_service                        u:object_r:contexthub_service:s0
+contexthub                                u:object_r:contexthub_service:s0
 country_detector                          u:object_r:country_detector_service:s0
 cpuinfo                                   u:object_r:cpuinfo_service:s0
 dbinfo                                    u:object_r:dbinfo_service:s0