Update unit-tests.md (#4979)

Grammar correction

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website/docs/docs/build/unit-tests.md

@@ -15,7 +15,7 @@ For dbt Core, unit tests will be available in v1.8, planned for late April 2024.
 
 :::
 
-Historically, dbt's test coverage was confined to [“data” tests](/docs/build/data-tests), assessing the quality of input data or resulting datasets' structure. However, these tests could only be executed _after_ a building a model. 
+Historically, dbt's test coverage was confined to [“data” tests](/docs/build/data-tests), assessing the quality of input data or resulting datasets' structure. However, these tests could only be executed _after_ building a model. 
 
 Now, we are introducing a new type of test to dbt - unit tests. In software programming, unit tests validate small portions of your functional code, and they work much the same way here. Unit tests allow you to validate your SQL modeling logic on a small set of static inputs _before_ you materialize your full model in production. Unit tests enable test-driven development, benefiting developer efficiency and code reliability.