output/pipewire: reset the "interrupted" flag in Cancel()

This fixes seeking.

src/output/plugins/PipeWireOutputPlugin.cxx

@@ -121,7 +121,7 @@ private:
 	size_t Play(const void *chunk, size_t size) override;
 
 	// TODO: void Drain() override;
-	// TODO: void Cancel() noexcept override;
+	 void Cancel() noexcept override;
 	// TODO: bool Pause() noexcept override;
 };
 
@@ -313,6 +313,15 @@ PipeWireOutput::Play(const void *chunk, size_t size)
 	}
 }
 
+void
+PipeWireOutput::Cancel() noexcept
+{
+	const PipeWire::ThreadLoopLock lock(thread_loop);
+	interrupted = false;
+
+	// TODO implement
+}
+
 const struct AudioOutputPlugin pipewire_output_plugin = {
 	"pipewire",
 	nullptr,