Update wrong documentation

"config" value is not necessary and leads to erro

Author: jonaschn

website/docs/reference/resource-configs/severity.md

@@ -46,12 +46,11 @@ models:
   - name: large_table
     columns:
       - name: slightly_unreliable_column
-        tests:
+        data_tests:
           - unique:
-              config:
-                severity: error
-                error_if: ">1000"
-                warn_if: ">10"
+              severity: error
+              error_if: ">1000"
+              warn_if: ">10"
 ```
 
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