man: remove period from description

Previously, scrypt(1) looked like:

    NAME
         scrypt – encrypt and decrypt files.

However, the final period was a mistake.  (I double-checked with a dozen
system utilities; none of them had a period there.)

Reported by:	mandoc -Tlint -Wstyle scrypt.1

scrypt.1

@@ -26,7 +26,7 @@
 .Os
 .Sh NAME
 .Nm scrypt
-.Nd encrypt and decrypt files.
+.Nd encrypt and decrypt files
 .Sh SYNOPSIS
 .Nm
 .Brq Cm enc | Cm dec | Cm info