use left join for joining current sprint info

[fivetran-jamie]

Are you a current Fivetran customer?

internal

What change(s) does this PR introduce?

• makes the join here a left join. this is necessary when the latest sprint value is truly null

Did you update the CHANGELOG?

• Yes
  not yet

Does this PR introduce a breaking change?

• Yes (please provide breaking change details below.)
• No (please provide an explanation as to how the change is non-breaking below.)

Did you update the dbt_project.yml files with the version upgrade (please leverage standard semantic versioning)? (In both your main project and integration_tests)

• Yes

Is this PR in response to a previously created Bug or Feature Request

• Yes, Issue/Feature [Bug] Current Sprint and Sprint not handling nulls well #91
• No

How did you test the PR changes?

• Buildkite
• Local (please provide additional testing details below)

Select which warehouse(s) were used to test the PR

• BigQuery
• Redshift
• Snowflake
• Postgres
• Databricks
• Other (provide details below)

Provide an emoji that best describes your current mood

🧨

Feedback

We are so excited you decided to contribute to the Fivetran community dbt package! We continue to work to improve the packages and would greatly appreciate your feedback on our existing dbt packages or what you'd like to see next.

[fivetran-joemarkiewicz]

@fivetran-jamie should we close this, or is this PR still relevant?