fallbacksrc: Don't apply fallback-audio-caps to the main audio stream

Intended behavior is configuring audio convert/resample elements
only for the fallback stream and also fallback-audio-caps is set.
Video and image stream are doing it as intended already.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/merge_requests/1213>

utils/fallbackswitch/src/fallbacksrc/imp.rs

@@ -1672,7 +1672,7 @@ impl FallbackSrc {
         filter_caps: &gst::Caps,
         fallback_source: bool,
     ) -> gst::Element {
-        if !fallback_source && filter_caps.is_any() {
+        if !fallback_source || filter_caps.is_any() {
             return gst::ElementFactory::make("identity")
                 .build()
                 .expect("No identity found");