aactab.h: update and correct comment

Tables in that file have been used by both for a long time now.
Signed-off-by: NRostislav Pehlivanov <atomnuker@gmail.com>

libavcodec/aactab.h

@@ -37,12 +37,11 @@
 
 #include <stdint.h>
 
-extern AVOnce aac_table_init; /* Protects ff_aac_tableinit() */
-
 /* NOTE:
- * Tables in this file are used by the AAC decoder and will be used by the AAC
- * encoder.
- */
+ * Tables in this file are shared by the AAC decoders and encoder */
+*/
+
+extern AVOnce aac_table_init; /* Protects ff_aac_tableinit() */
 
 /* @name ltp_coef
  * Table of the LTP coefficients