test: fix ion-R expected property format

Problem: t/t8001-util-ion-R.t expects JGF properties to be formatted
as a JSON array, but they are actually given by a mapping.

Fix the expected type.

t/t8001-util-ion-R.t

@@ -159,24 +159,24 @@ test_expect_success 'fluxion-R: can detect insufficient nodelist' '
 
 test_expect_success 'fluxion-R: encoding properties on heterogeneity works' '
     cat <<-EOF >expected6 &&
-	/cluster0 -1 []
-	/cluster0/foo2 0 ["arm-v9@core"]
-	/cluster0/foo2/core0 0 []
-	/cluster0/foo2/core1 0 []
-	/cluster0/foo2/gpu0 0 []
-	/cluster0/foo2/gpu1 0 []
-	/cluster0/foo3 2 ["arm-v9@core","amd-mi60@gpu"]
-	/cluster0/foo3/core0 2 []
-	/cluster0/foo3/core1 2 []
-	/cluster0/foo3/gpu0 2 []
-	/cluster0/foo3/gpu1 2 []
-	/cluster0/foo1 3 ["arm-v9@core","amd-mi60@gpu"]
-	/cluster0/foo1/core0 3 []
-	/cluster0/foo1/core1 3 []
-	/cluster0/foo1/gpu0 3 []
-	/cluster0/foo1/gpu1 3 []
-	/cluster0/foo4 1 ["arm-v8@core"]
-	/cluster0/foo4/core0 1 []
+	/cluster0 -1 {}
+	/cluster0/foo2 0 {"arm-v9@core":""}
+	/cluster0/foo2/core0 0 {}
+	/cluster0/foo2/core1 0 {}
+	/cluster0/foo2/gpu0 0 {}
+	/cluster0/foo2/gpu1 0 {}
+	/cluster0/foo3 2 {"arm-v9@core":"","amd-mi60@gpu":""}
+	/cluster0/foo3/core0 2 {}
+	/cluster0/foo3/core1 2 {}
+	/cluster0/foo3/gpu0 2 {}
+	/cluster0/foo3/gpu1 2 {}
+	/cluster0/foo1 3 {"arm-v9@core":"","amd-mi60@gpu":""}
+	/cluster0/foo1/core0 3 {}
+	/cluster0/foo1/core1 3 {}
+	/cluster0/foo1/gpu0 3 {}
+	/cluster0/foo1/gpu1 3 {}
+	/cluster0/foo4 1 {"arm-v8@core":""}
+	/cluster0/foo4/core0 1 {}
 	EOF
     flux R encode -r 0 -c 0-1 -g 0-1 -p "arm-v9@core:0" -H foo2 > out6 &&
     flux R encode -r 1 -c 0 -H foo3 -p "arm-v8@core:1" >> out6 &&