pthread_attr_setinheritsched.3: SYNOPSIS: Use 'restrict' in prototypes

pthread_attr_setinheritsched.3: SYNOPSIS: Use 'restrict' in prototypes

Both POSIX and glibc use 'restrict' in
pthread_attr_getinheritsched().
Let's use it here too.

.../glibc$ grep_glibc_prototype pthread_attr_getinheritsched
sysdeps/htl/pthread.h:90:
extern int pthread_attr_getinheritsched (const pthread_attr_t *__restrict __attr,
					 int *__restrict __inheritsched)
	__THROW __nonnull ((1, 2));
sysdeps/nptl/pthread.h:313:
extern int pthread_attr_getinheritsched (const pthread_attr_t *__restrict
					 __attr, int *__restrict __inherit)
     __THROW __nonnull ((1, 2));
.../glibc$

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