Fix typo

Author: MCUdude

src/avrdude.1

@@ -2076,7 +2076,7 @@ Show help menu and exit.
 .Ss Programmers accepting exitspec parameter
 Currently, only the flip2, linuxspi, linuxgpio, raspberry_pi_gpio and old school parallel
 port programmers such as stk200 and dapa support exitspec parameter.
-These lets the user decide in which state the programmer pins after ended programming session.
+These let the user decide in which state the programmer pins after ended programming session.
 Multiple exitspec options can be separated with commas.
 .Bl -tag -offset indent -width indent
 .It Ar flip2