getpriority.2: Remove unused include

<sys/time.h> is not needed to get the function declaration nor any
constant used by the function.  It was only needed (before
POSIX.1) to get 'struct timeval', but that information would be
more suited for system_data_types(7), and not for this page.

Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man2/getpriority.2

@@ -47,7 +47,6 @@
 getpriority, setpriority \- get/set program scheduling priority
 .SH SYNOPSIS
 .nf
-.B #include <sys/time.h>
 .B #include <sys/resource.h>
 .PP
 .BI "int getpriority(int " which ", id_t " who );
@@ -209,18 +208,6 @@ the real or effective user ID of the process \fIwho\fP.
 All BSD-like systems (SunOS 4.1.3, Ultrix 4.2,
 4.3BSD, FreeBSD 4.3, OpenBSD-2.5, ...) behave in the same
 manner as Linux 2.6.12 and later.
-.PP
-Including
-.I <sys/time.h>
-is not required these days, but increases portability.
-(Indeed,
-.I <sys/resource.h>
-defines the
-.I rusage
-structure with fields of type
-.I struct timeval
-defined in
-.IR <sys/time.h> .)
 .\"
 .SS C library/kernel differences
 Within the kernel, nice values are actually represented