Fix performance of variant analysis view

When the variant analysis view was being rerendered, we were also
reregistering the message listeners, while not deregistering the old
ones. This resulted in a loop of message listeners being registered,
and the variant analysis being rerendered every time a message was
received by one of the listeners. This will ensure that the listener
is only registered once to prevent this from happening.

extensions/ql-vscode/src/view/variant-analysis/VariantAnalysis.tsx

@@ -90,7 +90,7 @@ export function VariantAnalysis({
         console.error(`Invalid event origin ${origin}`);
       }
     });
-  });
+  }, []);
 
   if (variantAnalysis?.actionsWorkflowRunId === undefined) {
     return <VariantAnalysisLoading />;