bspatch.1: fix missing argument

Fix typo

MFC after:	3 days
Reviewed by:	gbe
Differential Revision:	https://reviews.freebsd.org/D37727

usr.bin/bsdiff/bspatch/bspatch.1

@@ -25,7 +25,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd May 18, 2003
+.Dd December 22, 2022
 .Dt BSPATCH 1
 .Os
 .Sh NAME
@@ -83,4 +83,5 @@ Users may also wish to verify after running
 that
 .Ar newfile
 matches the target file from which
-.Ar was built.
+.Ar patchfile
+was built.