Update README.txt

Fix typo

Author: jogo-

build/windows/dist/drivers/README.txt

@@ -2,6 +2,6 @@
 With this version of Arduino a new all-in-one driver (with
 security signature for Windows 8) is supplied.
 
-The old (deprected) drivers are still available in the
+The old (deprecated) drivers are still available in the
 Old_Arduino_Drivers.zip