lavf: Don't explicitly flush after each written packet in muxers

Since 596e5d4783, this is not necessary anymore. It also allows to
actually disable the flushing, improving write performance (but
possibly giving worse latency in real-time streaming).

Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/wvenc.c

@@ -51,7 +51,6 @@ static int wv_write_packet(AVFormatContext *ctx, AVPacket *pkt)
     s->samples += header.samples;
 
     avio_write(ctx->pb, pkt->data, pkt->size);
-    avio_flush(ctx->pb);
 
     return 0;
 }