tools/create-gce-image.sh: drop rodata=n

There is suspicion that the random programs corrupt .text segment:
https://groups.google.com/g/syzkaller-bugs/c/d5GC1V8S34k/m/6LTarP8mBAAJ
which leads to a number of assorted confusing crashes:
https://syzkaller.appspot.com/bug?extid=ce179bc99e64377c24bc

Turns out we disable text ro protection with rodata=n.
The comment says that's because it's slow with KASAN,
but most likely what was slow is actually additional
debug checking due to CONFIG_DEBUG_WX.
If we don't enable CONFIG_DEBUG_WX (which we don't),
rodata itself should be fine and desirable.

My experiment with the latest kernel does not show
any noticable slowdown without rodata=n:

[   11.985152][    T1] Freeing unused kernel image (initmem) memory: 3432K
[   11.986129][    T1] Write protecting the kernel read-only data: 147456k
[   11.990863][    T1] Freeing unused kernel image (text/rodata gap) memory: 2012K
[   11.992797][    T1] Freeing unused kernel image (rodata/data gap) memory: 1324K
[   11.993895][    T1] Run /sbin/init as init process

[   11.910396][    T1] Freeing unused kernel image (initmem) memory: 3432K
[   11.911277][    T1] Kernel memory protection disabled.
[   11.911984][    T1] Run /sbin/init as init process

0 files changed, 0 insertions, 0 deletions