deps/media-playback: Use avcodec_free_context when possible

A bit better handling that should prevent any possible memory leakage
due to any internal data allocated by FFmpeg.

deps/media-playback/media-playback/decode.c

@@ -167,9 +167,10 @@ void mp_decode_free(struct mp_decode *d)
 	circlebuf_free(&d->packets);
 
 	if (d->decoder) {
-		avcodec_close(d->decoder);
 #if LIBAVFORMAT_VERSION_INT >= AV_VERSION_INT(57, 40, 101)
-		av_free(d->decoder);
+		avcodec_free_context(&d->decoder);
+#else
+		avcodec_close(d->decoder);
 #endif
 	}