Floss: remove unused library avformat

This CL removes the unused library to minimize required package size.

Bug: 314227872
Test: m Bluetooth
Flag: EXEMPT floss only changes
Change-Id: Ia9745b6bdf1ec9cf60f4a65eedced1c945128863

system/stack/mmc/codec_server/BUILD.gn

@@ -33,7 +33,6 @@ source_set("libcodec_server_a2dp_aac") {
   libs = [
     # Following are for AAC using FFmpeg
     "avcodec",
-    "avformat",
     "avutil",
   ]
 }