fix: update indexes-constraints page pgTable to the correct signature

[hill]

#433 updated these docs to the new signature in 0.36.0, where

...
  (table) => ({
    constraint: unique().on(table.something)
  })
)

becomes:

...,
  (table) => [
    unique().on(table.something)
  ]
)

but it left the PgTableExtraConfig in the array, which is incorrect and results in drizzle-kit not generating migrations. (i.e was updated to:

...,
  (table) => [{
    constraint: unique().on(table.something)
  }]
)

)

As per the mentioned diff, I believe it should be PgTableExtraConfigValue[] not PgTableExtraConfig[]

Let me know if I've misunderstood this and thanks for your time 🤗

Closes #456

[hill]

I believe this PR also closes #456

[jasongerbes]

Related Drizzle ORM issues:

• [BUG]: Migrations are not generated for new Indexes drizzle-orm#3873
• [BUG]:Composite primary key not added to postgres schema when using array return in pgTable drizzle-orm#3596

I believe this docs change also needs to be applied to the other dialects (MySQL, SQLite, and SingleStore), as the object syntax has been replaced by the array syntax for those too.