doc/examples/muxing: free swr context at the end

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

doc/examples/muxing.c

@@ -547,6 +547,7 @@ static void close_stream(AVFormatContext *oc, OutputStream *ost)
     av_frame_free(&ost->frame);
     av_frame_free(&ost->tmp_frame);
     sws_freeContext(ost->sws_ctx);
+    swr_free(&ost->swr_ctx);
 }
 
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