Update benchmark.mdx

Author: robertjdominguez

docs/reference/benchmark.mdx

@@ -91,7 +91,7 @@ limitations, and in particular against output token limits.
 PromptQL's key insight is that intelligence is required to create a query plan, but is not required to execute the query
 plan. The execution of the query plan should be mechanical and 100% repeatable.
 
-PromptQL's query plans are composed of steps that are computational and cognitive. These ensures intelligence can be
+PromptQL's query plans are composed of steps that are computational and cognitive. These ensure intelligence can be
 precisely used only in the isolated context of the step (eg: "extract project_id from the ticket description").
 
 ```mermaid