mpegts: Always re-export the contents of the auto module

Pre-1.20 it currently has nothing to re-export and would cause clippy
warnings, but like this it won't be forgotten to update the conditions
if new API is added that is available from older versions.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer-rs/-/merge_requests/1414>

gstreamer-mpegts/src/lib.rs

@@ -22,6 +22,7 @@ pub fn init() {
     assert_initialized_main_thread!();
 }
 
-// Workaround for https://github.com/gtk-rs/gir/issues/1555.
 #[allow(unused_imports)]
 mod auto;
+#[allow(unused_imports)]
+pub use crate::auto::*;