Update flac.md - and reworded -M

Author: H2Swine

man/flac.md

@@ -425,8 +425,7 @@ Encoding will default to -5, -A "tukey(5e-1)" and one CPU thread.
 	select the best compression. (Stereo only, ignored otherwise.)
 
 **-M**, **\--adaptive-mid-side**
-:	Adaptive choice of mid-side coding (stereo only, ignored otherwise);
-	faster than -m, but slightly weaker compression.
+:	Like -m, but adaptive choice (faster, slightly weaker compression).
 
 **-r** \[\#,\]\#, **\--rice-partition-order**=\[\#,\]\#
 :	Set the \[min,\]max residual partition order (0..15). For subset