doc/muxers: fix typo of the hls var_stream_map example

And fix typo of the 1833 of hlsenc.c
Reviewed-by: Gyan Doshi <ffmpeg@gyani.pro>
Signed-off-by: Steven Liu <lq@onvideo.cn>

doc/muxers.texi

@@ -991,7 +991,7 @@ By default, a single hls variant containing all the encoded streams is created.
 @example
 ffmpeg -re -i in.ts -b:a:0 32k -b:a:1 64k -b:v:0 1000k \
   -map 0:a -map 0:a -map 0:v -f hls \
-  -var_stream_map "a:0,agroup:aud_low,default:yes,language=ENG a:1,agroup:aud_low,language:CHN v:0,agroup:aud_low" \
+  -var_stream_map "a:0,agroup:aud_low,default:yes,language:ENG a:1,agroup:aud_low,language:CHN v:0,agroup:aud_low" \
   -master_pl_name master.m3u8 \
   http://example.com/live/out_%v.m3u8
 @end example

libavformat/hlsenc.c

@@ -1830,7 +1830,7 @@ static int parse_variant_stream_mapstring(AVFormatContext *s)
     /**
      * Expected format for var_stream_map string is as below:
      * "a:0,v:0 a:1,v:1"
-     * "a:0,agroup:a0,default:1,language:ENG a:1,agroup:a1,defalut:0 v:0,agroup:a0  v:1,agroup:a1"
+     * "a:0,agroup:a0,default:1,language:ENG a:1,agroup:a1,default:0 v:0,agroup:a0  v:1,agroup:a1"
      * This string specifies how to group the audio, video and subtitle streams
      * into different variant streams. The variant stream groups are separated
      * by space.