Update the refs to reflect individual adapters moving into `dbt-adapters` monorepo

[dbeatty10]

Describe the bug

dbt-postgres moved to the dbt-adapters monorepo. We need to update the refs so that they don't point to a stale version of dbt-postgres.

See dbt-labs/dbt-adapters#615 for more detail.

Next steps

Replace anything like this:

git+https://github.com/dbt-labs/dbt-postgres.git@main#egg=dbt-postgres

with this:

git+https://github.com/dbt-labs/dbt-adapters.git@main#subdirectory=dbt-postgres

e.g.,

dbt-utils/dev-requirements.txt

Line 5 in 5c9dc0d

dbt-postgres@git+https://github.com/dbt-labs/dbt-postgres.git