Update minimum supported Rust version to 1.80

In preparation of doing the same in gstreamer-rs.

audio/audiofx/src/audioecho/mod.rs

@@ -13,7 +13,7 @@ mod imp;
 mod ring_buffer;
 
 glib::wrapper! {
-    pub struct AudioEcho(ObjectSubclass<imp::AudioEcho>) @extends gst_base::BaseTransform, gst::Element, gst::Object;
+    pub struct AudioEcho(ObjectSubclass<imp::AudioEcho>) @extends gst_audio::AudioFilter, gst_base::BaseTransform, gst::Element, gst::Object;
 }
 
 pub fn register(plugin: &gst::Plugin) -> Result<(), glib::BoolError> {