whitepaper link fix

Author: nidhi-singh02

apps/developer-hub/content/docs/metrics/publisher-metrics.mdx

@@ -19,7 +19,7 @@ The **uptime graph** shows when the publisher was actively contributing prices.
 
 **Quality**
 
-The quality graph shows the dataset used in the regression model for computing the quality score described in section 4.1.1 of the [whitepaper](https://pyth.network/whitepaper.pdf). The quality score measures how well a publisher's price series predicts future changes in the aggregate price. A smooth color gradient (from blue on the bottom left to pink on the top right) indicates a high-quality score.
+The quality graph shows the dataset used in the regression model for computing the quality score described in section 4.1.1 of the [whitepaper](https://pyth.network/whitepaper). The quality score measures how well a publisher's price series predicts future changes in the aggregate price. A smooth color gradient (from blue on the bottom left to pink on the top right) indicates a high-quality score.
 
 ![Quality](/images/publisher-metrics/Quality.jpg)