Flag handling snippet in playbin example is outdated

To reproduce, uncomment this snippet (I've used 2a9d0d03) and run cargo check --bin playbin:

error[E0599]: no method named `get_property` found for struct `gstreamer::Element` in the current scope
  --> examples/src/bin/playbin.rs:40:25
   |
40 |     let flags = playbin.get_property("flags").unwrap();
   |                         ^^^^^^^^^^^^ method not found in `Element`

error[E0061]: this function takes 0 arguments but 1 argument was supplied
   --> examples/src/bin/playbin.rs:41:23
    |
41  |     let flags_class = FlagsClass::new(flags.type_()).unwrap();
    |                       ^^^^^^^^^^^^^^^ -------------
    |                                       |
    |                                       unexpected argument
    |                                       help: remove the extra argument
    |
note: associated function defined here
   --> /home/naglis/.cargo/git/checkouts/gtk-rs-core-7be42ca38bd6361c/dc264f6/glib/src/enums.rs:421:12
    |
421 |     pub fn new<T: StaticType + HasParamSpec<ParamSpec = ParamSpecFlags>>() -> Self {
    |            ^^^

error[E0599]: no method named `unwrap` found for struct `FlagsClass` in the current scope
  --> examples/src/bin/playbin.rs:41:54
   |
41 |     let flags_class = FlagsClass::new(flags.type_()).unwrap();
   |                                                      ^^^^^^ method not found in `FlagsClass`

error[E0599]: no method named `unwrap` found for unit type `()` in the current scope
  --> examples/src/bin/playbin.rs:49:54
   |
49 |     playbin.set_property_from_value("flags", &flags).unwrap();
   |                                                      ^^^^^^ method not found in `()`

Some errors have detailed explanations: E0061, E0599.
For more information about an error, try `rustc --explain E0061`.

FWIW, I've got it working again via these changes:

-    // let flags = playbin.get_property("flags").unwrap();
-    // let flags_class = FlagsClass::new(flags.type_()).unwrap();
+    // let flags = playbin.property_value("flags");
+    // let flags_class = FlagsClass::with_type(flags.type_()).unwrap();
     // let flags = flags_class.builder_with_value(flags).unwrap()
     //     .unset_by_nick("text")
     //     .unset_by_nick("video")
     //     .build()
     //     .unwrap();
-    // playbin.set_property_from_value("flags", &flags).unwrap();
+    // playbin.set_property_from_value("flags", &flags);