fix(memory-tracker): remove unused variable in calculateTrend method

Author: mceachen

benchmark/memory-tracker.ts

@@ -208,7 +208,6 @@ export class MemoryTracker {
     const sumY = values.reduce((a, b) => a + b, 0);
     const sumXY = x.reduce((sum, xi, i) => sum + xi * values[i], 0);
     const sumX2 = x.reduce((sum, xi) => sum + xi * xi, 0);
-    const sumY2 = values.reduce((sum, yi) => sum + yi * yi, 0);
 
     const slope = (n * sumXY - sumX * sumY) / (n * sumX2 - sumX * sumX);
     const intercept = (sumY - slope * sumX) / n;