doc(man): add a hint about which UI element is the finder info (#2991)

While reading the description of the --info flag, it's not
immediately obvious that the "finder info" is in fact the
UI element representing the match counters.

man/man1/fzf.1

@@ -281,7 +281,7 @@ e.g.
 
 .TP
 .BI "--info=" "STYLE"
-Determines the display style of finder info.
+Determines the display style of finder info (match counters).
 
 .br
 .BR default "       Display on the next line to the prompt"