man: fix docs about edge mode

it no longer ignores -f flag since
c60a26c

Author: N-R-K

man/scrot.txt

@@ -170,8 +170,8 @@ SELECTION STYLE
     mode=MODE       MODE can be "auto", "edge" or "classic" without quotes.
                     edge is the new selection, classic uses the old one.
                     "auto" uses "edge" if no compositor is running, "classic"
-                    otherwise. "edge" ignores the style specifier and the -f flag,
-                    "classic" ignores the opacity specifier.
+                    otherwise. "edge" ignores the style specifier, "classic"
+                    ignores the opacity specifier.
 
   Without the -l option, a default style is used: