move the SSA/ASS codecprivate in the Initialization section

(similar to ietf-wg-cellar#446)

Co-authored-by: Jérôme Martinez <jerome@mediaarea.net>

Author: robUx4

codec_specs.md

@@ -1020,11 +1020,13 @@ Codec ID: S_TEXT/ASS
 
 Codec Name: Advanced SubStation Alpha Format
 
-Description: The [Script Info] and [V4 Styles] sections are stored in the codecprivate. Each event is stored in its own `Block`.
+Description: Each event is stored in its own `Block`.
 For more information see (#ssa-ass-subtitles) on SSA/ASS.
 
 The codec **MAY** also be found with the Codec ID `S_ASS`, but using that value is **NOT RECOMMENDED**.
 
+Initialization: The "[Script Info]" and "[V4 Styles]" sections are stored in the `CodecPrivate`.
+
 ### S_TEXT/ASCII
 
 Codec ID: S_TEXT/ASCII
@@ -1039,11 +1041,13 @@ Codec ID: S_TEXT/SSA
 
 Codec Name: SubStation Alpha Format
 
-Description: The [Script Info] and [V4 Styles] sections are stored in the codecprivate. Each event is stored in its own `Block`.
+Description: Each event is stored in its own `Block`.
 For more information see (#ssa-ass-subtitles) on SSA/ASS.
 
 The codec **MAY** also be found with the Codec ID `S_SSA`, but using that value is **NOT RECOMMENDED**.
 
+Initialization: The "[Script Info]" and "[V4+ Styles]" sections are stored in the `CodecPrivate`.
+
 ### S_TEXT/USF
 
 Codec ID: S_TEXT/USF