Add 2019.6 feature

rust-bindings/rust/Cargo.toml

@@ -82,4 +82,5 @@ v2018_9 = ["v2018_7", "ostree-sys/v2018_9"]
 v2019_2 = ["v2018_9", "ostree-sys/v2019_2"]
 v2019_3 = ["v2019_2", "ostree-sys/v2019_3"]
 v2019_4 = ["v2019_3", "ostree-sys/v2019_4"]
-latest = ["v2019_4"]
+v2019_6 = ["v2019_4", "ostree-sys/v2019_6"]
+latest = ["v2019_6"]