test: remove checks for 'rabbits' event context

Problem: the 'rabbits' entry in the 'dws_environment' eventlog
entry has been removed, but tests still expect it.

Remove tests for it.

t/t1002-dws-workflow-obj.t

@@ -164,7 +164,7 @@ test_expect_success 'job submission with valid DW string works' '
 		${jobid} prolog-finish &&
 	flux job wait-event -vt 15 -m status=0 ${jobid} finish &&
 	flux job wait-event -t1 -fjson ${jobid} dws_environment > env-event.json &&
-	jq -e .context.variables env-event.json && jq -e .context.rabbits env-event.json &&
+	jq -e .context.variables env-event.json &&
 	jq -e ".context.copy_offload == false" env-event.json &&
 	flux job wait-event -vt 15 -m description=${EPILOG_NAME} \
 		${jobid} epilog-start &&
@@ -206,7 +206,7 @@ test_expect_success 'job requesting copy-offload in DW string works' '
 		${jobid} prolog-finish &&
 	flux job wait-event -vt 15 -m status=0 ${jobid} finish &&
 	flux job wait-event -t1 -fjson ${jobid} dws_environment > env-event2.json &&
-	jq -e .context.variables env-event2.json && jq -e .context.rabbits env-event2.json &&
+	jq -e .context.variables env-event2.json &&
 	jq -e ".context.copy_offload == true" env-event2.json &&
 	flux job wait-event -vt 15 -m description=${EPILOG_NAME} \
 		${jobid} epilog-start &&