Fix util-db update --validate flag

[matejmode]

Validate during update doesn't load db-hash correctly.

build/util-db update --chainid 1 --log debug --validate --db-tmp tmp/ --aida-db aida-db
...
2023/12/09 18:53:06 CRITICAL: DbHash not found in downloaded Patch - cannot perform validation. If you were missing only lachesis patch, this would be normal behaviour.
...

[matejmode]

This is not priority error as it doesn't corrupt the database, and validation can be run right after getting this error.

[wsodsong]

Can you give a bit more information about this issue? What is the latest patch name or last block number or expected db-hash?

[matejmode]

The issue is that just during the update wrong db-hash is loaded to be compared against freshly downloaded patch. So there is an error. While everything else being correct. And even right after downloading with this fail you can correctly do util-db validate so this is not any blocking issue.

[wsodsong]

Since we already have util-db validate command. I like to suggest remove --validate option from util-db update command. We can always run util-db validate afterwards.