Remove loglevel=3 for isomaker cfgs (#6891)

toolkit/resources/assets/isomaker/iso_root_arch-dependent_files/amd64/isolinux/isolinux.cfg

@@ -4,4 +4,4 @@ totaltimeout 1
 default Installer
 label Installer
 	kernel vmlinuz
-	append initrd=initrd.img root=/dev/ram0 loglevel=3 console=tty0 console=ttyS0,115200n8
+	append initrd=initrd.img root=/dev/ram0 console=tty0 console=ttyS0,115200n8

toolkit/resources/assets/isomaker/iso_root_static_files/boot/grub2/grub.cfg

@@ -4,6 +4,6 @@ set timeout=0
 # but it is observed to be needed to boot on some hardware/SoCs.
 menuentry "CBL-Mariner" {
     search --label CDROM --set root
-    linux /isolinux/vmlinuz root=/dev/ram0 loglevel=3 mariner.media=CDROM lockdown=integrity sysctl.kernel.unprivileged_bpf_disabled=1 console=tty0 console=ttyS0,115200n8
+    linux /isolinux/vmlinuz root=/dev/ram0 mariner.media=CDROM lockdown=integrity sysctl.kernel.unprivileged_bpf_disabled=1 console=tty0 console=ttyS0,115200n8
     initrd /isolinux/initrd.img
 }