msg: Remove redundant #include <sys/msg.h> header

The #include <sys/msg.h> is redundant as we do not use message specific
types for issuing syscalls to handle msg and shm. Only msgctl requires
this header.

Build tests:
./src/scripts/build-many-glibcs.py glibcs

sysdeps/unix/sysv/linux/msgget.c

@@ -16,7 +16,6 @@
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
-#include <sys/msg.h>
 #include <ipc_priv.h>
 #include <sysdep.h>
 #include <errno.h>

sysdeps/unix/sysv/linux/msgrcv.c

@@ -16,7 +16,6 @@
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
-#include <sys/msg.h>
 #include <ipc_priv.h>
 #include <sysdep-cancel.h>
 

sysdeps/unix/sysv/linux/msgsnd.c

@@ -16,7 +16,6 @@
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
-#include <sys/msg.h>
 #include <ipc_priv.h>
 #include <sysdep-cancel.h>
 

sysdeps/unix/sysv/linux/shmat.c

@@ -16,7 +16,6 @@
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
-#include <sys/msg.h>
 #include <ipc_priv.h>
 #include <sysdep.h>
 #include <errno.h>

sysdeps/unix/sysv/linux/shmdt.c

@@ -16,7 +16,6 @@
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
-#include <sys/msg.h>
 #include <ipc_priv.h>
 #include <sysdep.h>
 #include <errno.h>

sysdeps/unix/sysv/linux/shmget.c

@@ -16,7 +16,6 @@
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
-#include <sys/msg.h>
 #include <ipc_priv.h>
 #include <sysdep.h>
 #include <errno.h>