fix: adjust aws_c5.18xlarge memory size

[clumsy]

MEM_TAX is not enough to adjust memory size for the actual memory we get:

              total        used        free      shared  buff/cache   available
Mem:      144113336     1443996   140375536         812     2293804   141697752
Swap:             0           0           0

Test plan:

• Submitted a training job using 142 * GiB

[clumsy]

Please let me know if this needs to be updated, @kiukchung. Thanks!

[clumsy]

Could you please check this small PR, @kiukchung @d4l3k?

[kiukchung]

I seem to have lost approve/merge/run-workflow access to this repo... cc) @d4l3k @yikaiMeta

[clumsy]

Could you please have a look, @tonykao8080?

[tonykao8080]

looks good

[clumsy]

Thanks @tonykao8080 let me amend+force-push to kick-start that linter check

[clumsy]

My bad, @tonykao8080 used main for my other PR also (last time not using feature branches 😁).

This time the change is right and hopefully the linter will start too.

[clumsy]

This should pass the linter now, @tonykao8080

[clumsy]

@kiukchung @tonykao8080 With the change being approved and the failure in Docs Builder being unrelated. Is there anything else left to do before we can merge this PR? Thanks!