warn again about raw format in README

Author: jmvalin

README

@@ -29,6 +29,7 @@ PCM files sampled at 48 kHz. It can be used as:
 ./examples/rnnoise_demo <noisy speech> <output denoised>
 
 The output is also a 16-bit raw PCM file.
+NOTE AGAIN, THE INPUT and OUTPUT ARE IN RAW FORMAT, NOT WAV.
 
 The latest version of the source is available from
 https://gitlab.xiph.org/xiph/rnnoise .  The github repository