Migrate to `Protobuf>=5.26.0,<6`

[QMalcolm]

Housekeeping

• [X] I am a maintainer of dbt-core

Short description

We're currently depend on protobuf 4.y.z, and protobuf 5 is coming out soon. Thus far they've released three release candidates (5.26.0-rc1, 5.26.0-rc2, 5.26.0rc-3). We don't know exactly when the 5.26.0 production release will happen. However, if history is any indicator, it'll probably be out by the end of March 2024 (less than a month). It's hard to say how long it will take for the python community at large to migrate, but we should be prepared to do so.

Acceptance criteria

• dbt-core depends on protobuf v5
• dbt-core doesn't depend on protobuf v4

Suggested Tests

The current tests should still pass

Impact to Other Teams

None

Will backports be required?

No

Context

No response