cp: Correct description of SIGINFO

The manual page claimed that SIGINFO caused information to be printed to
stdout, when in fact it is printed to stderr, as one would expect.  This
has been true ever since the feature was first added in 2003.

MFC after:	1 week
Fixes:		00d321a2b3 ("Add a SIGINFO handler.")
Reviewed by:	jilles
Differential Revision:	https://reviews.freebsd.org/D58392

bin/cp/cp.1

@@ -29,7 +29,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd June 9, 2026
+.Dd July 22, 2026
 .Dt CP 1
 .Os
 .Sh NAME
@@ -269,7 +269,7 @@ receives a
 argument for
 .Xr stty 1 )
 signal, the current input and output file and the percentage complete
-will be written to the standard output.
+will be written to the standard error output.
 .Sh EXIT STATUS
 .Ex -std
 .Sh EXAMPLES