Drop unused arguments from README (#103)

Match wording given by usage.

Author: dvisockas

README

@@ -12,7 +12,7 @@ While it is meant to be used as a library, a simple command-line tool is
 provided as an example. It operates on RAW 16-bit (machine endian) mono
 PCM files sampled at 48 kHz. It can be used as:
 
-./examples/rnnoise_demo <number of channels> <maximum attenuation> < input.raw > output.raw
+./examples/rnnoise_demo <noisy speech> <output denoised>
 
 The output is also a 16-bit raw PCM file.