lavf/hls: Cleanup the applehttp

Cleanup the applehttp as demuxer name, when use the command :

ffmpeg -formats, get the confused information like:
"
 E hls             Apple HTTP Live Streaming
D  hls,applehttp   Apple HTTP Live Streaming
"
we don't use applehttp as the demuxer/muxer name usually, so
cleanup the applehttp and update the documents.

After the change, get the information from "ffmpeg -formats":
"
DE hls             Apple HTTP Live Streaming
"
Reviewed-by: Steven Liu <lq@onvideo.cn>
Signed-off-by: Jun Zhao <barryjzhao@tencent.com>

doc/demuxers.texi

@@ -25,17 +25,6 @@ Audible Format 2, 3, and 4 demuxer.
 
 This demuxer is used to demux Audible Format 2, 3, and 4 (.aa) files.
 
-@section applehttp
-
-Apple HTTP Live Streaming demuxer.
-
-This demuxer presents all AVStreams from all variant streams.
-The id field is set to the bitrate variant index number. By setting
-the discard flags on AVStreams (by pressing 'a' or 'v' in ffplay),
-the caller can decide which variant streams to actually receive.
-The total bitrate of the variant that the stream belongs to is
-available in a metadata key named "variant_bitrate".
-
 @section apng
 
 Animated Portable Network Graphics demuxer.
@@ -320,6 +309,15 @@ infinitely.
 
 HLS demuxer
 
+Apple HTTP Live Streaming demuxer.
+
+This demuxer presents all AVStreams from all variant streams.
+The id field is set to the bitrate variant index number. By setting
+the discard flags on AVStreams (by pressing 'a' or 'v' in ffplay),
+the caller can decide which variant streams to actually receive.
+The total bitrate of the variant that the stream belongs to is
+available in a metadata key named "variant_bitrate".
+
 It accepts the following options:
 
 @table @option

libavformat/hls.c

@@ -2318,14 +2318,14 @@ static const AVOption hls_options[] = {
 };
 
 static const AVClass hls_class = {
-    .class_name = "hls,applehttp",
+    .class_name = "hls demuxer",
     .item_name  = av_default_item_name,
     .option     = hls_options,
     .version    = LIBAVUTIL_VERSION_INT,
 };
 
 AVInputFormat ff_hls_demuxer = {
-    .name           = "hls,applehttp",
+    .name           = "hls",
     .long_name      = NULL_IF_CONFIG_SMALL("Apple HTTP Live Streaming"),
     .priv_class     = &hls_class,
     .priv_data_size = sizeof(HLSContext),