Docs: Fix maglev.hashSeed byte size documentation

[gaffneyd4]

Update documentation on maglev hash seed to instruct users to generate a 12 byte seed (instead of 16 bytes), according to this error message from cilium v1.9.4 (when a 16 byte seed had been used):

Failed to initialize maglev hash seeds: Decoded hash seed is 16 bytes (not 12 bytes)

[qmonnet]

Thanks a lot for the PR!

But I don't know if the change is correct. Looking at the history, I see that commit 4d9167f explicitly changed from 16 to 12 bytes, so the 16 byte length may apply to the base64 output and not to the initial bytes piped into base64? /Cc @brb

In any case one of the commands is wrong (either -c12 or -c16) and the text may need some clarification indeed, so thanks for working on this!

[Edit] You edited your PR while I was writing the review, and it looks good now I think. Asking a review from Martynas to be sure, but looks good from my side, thank you!

[brb]

The maglev hash seed is 16 bytes long. See:

$ head -c12 /dev/urandom | base64 -w0 | wc -c
16

[brb]

Scratch my previous comment.

[pchaigno]

Documentation-only change so fine to merge despite merge freeze.