resizewin.1: Fix option list width typo + spdx

MFC after:		3 days
Accepted by:		mhorne (mentor)
Differential Revision:	https://reviews.freebsd.org/D48349

(cherry picked from commit 4a5d51e73e)

usr.bin/resizewin/resizewin.1

@@ -1,3 +1,6 @@
+.\"
+.\" SPDX-License-Identifier: BSD-2-Clause
+.\"
 .\" resizewin
 .\"
 .\" Query terminal for size and inform the kernel
@@ -44,7 +47,7 @@ the size known to the kernel using the
 ioctl.
 .Pp
 The following options are available:
-.Bl -tag -width ".Fl z"
+.Bl -tag -width "-z"
 .It Fl z
 Do nothing unless the current kernel terminal size is zero.
 This is useful when run from a user's profile (shell startup) scripts: