docs: don't recommend 'for all tables' publication for source-postgres

[williamhbaker]

Description:

Doc updates for estuary/connectors#690. See that PR description for the technical background.

For manual setups these updated docs will instruct the user to create a targeted publication including only the tables they want to capture from rather than a "FOR ALL TABLES" publication which may have unwanted side effects.

Workflow steps:

(How does one use this feature, and how has it changed)

Documentation links affected:

(list any documentation links that you created, or existing ones that you've identified as needing updates, along with a brief description)

Notes for reviewers:

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This change is 

[willdonnelly]

LGTM

I think that it might still be worth noting somewhere on the page that the user can CREATE PUBLICATION ... FOR ALL TABLES in some circumstances, because adding tables individually can be a huge permissioning-related pain in some setups (AFAIK the query ALTER PUBLICATION ... ADD TABLE ... must be run either by a user with ownership of both the table and the publication, or by the database superuser, and transferring ownership after a table has been created is just a mess).

But on reflection I agree with Johnny's point about automatically breaking your database -- for the recommended sequences of copy-pastable setup commands here it's probably better to recommend the less dangerous approach, since either will work perfectly fine if you're doing this setup as the database superuser.

[oliviamiannone]

lgtm from the writing side!