[CT-2697] Can't use integers in measure expr

[Jstein77]

Is this a new bug in dbt-core?

• I believe this is a new bug in dbt-core
• I have searched the existing issues, and I could not find an existing issue for this bug

Current Behavior

Can’t use 1 in expr. A measure like below will yield the following error: 1 is not valid under any of the given schemas

- name: orders
        expr: 1
        agg: sum

Expected Behavior

I should be able to use integers in expr key.

Steps To Reproduce

Create a measure like below and run dbt run

- name: orders
        expr: 1
        agg: sum

Relevant log output

No response

Environment

- OS:
- Python:
- dbt:

Which database adapter are you using with dbt?

No response

Additional Context

No response

[Jstein77]

cc @QMalcolm