Bump minimum dbt-adapters requirement to 1.9.0

[QMalcolm]

Resolves #10996

Problem

In dbt-core we've made a switch from an environment variable for gating microbatch functionality to a project flag (#10799). In dbt-adapters we've done likewise (dbt-labs/dbt-adapters#323). For everything to work properly, we need depend on those changes in dbt-adapters, which will go out in 1.12.0

Solution

bump dbt-core's requirement spec for dbt-adapters to have a minimum of 1.12.0

Checklist

• I have read the contributing guide and understand what's expected of me.
• I have run this code in development, and it appears to resolve the stated issue.
• This PR includes tests, or tests are not required or relevant for this PR.
• This PR has no interface changes (e.g., macros, CLI, logs, JSON artifacts, config files, adapter interface, etc.) or this PR has already received feedback and approval from Product or DX.
• This PR includes type annotations for new and modified functions.

[QMalcolm]

Tests won't pass until we do the dbt-adapters release