keyboardModifiers: Implement review suggestion

Reduce unnecessary verbosity.

Co-authored-by: per1234 <accounts@perglass.com>

Author: edgar-bonet

Language/Functions/USB/Keyboard/keyboardModifiers.adoc

@@ -144,7 +144,7 @@ The library can simulate function keys up to F24.
 
 [float]
 ==== Function control keys
-These are three rarely used keys that sit above the navigation cluster.
+These are three keys that sit above the navigation cluster.
 
 |===
 |Key	|Hexadecimal value	|Decimal value	|Notes