audioloudnorm: Allow more than 2 channels

There's no limitation of the number of channels in the code, so allow
more in the caps too.

gst-plugin-audiofx/src/audioloudnorm.rs

@@ -1793,7 +1793,7 @@ impl ObjectSubclass for AudioLoudNorm {
             &[
                 ("format", &gst_audio::AUDIO_FORMAT_F64.to_str()),
                 ("rate", &192_000i32),
-                ("channels", &gst::IntRange::<i32>::new(1, 2)),
+                ("channels", &gst::IntRange::<i32>::new(1, std::i32::MAX)),
                 ("layout", &"interleaved"),
             ],
         );