Fix broken link to pro-guard file
Summary:
The proguard file got moved in which broke a link on the website. Updating the link to the new location of the file.
Closes
@@ -10,7 +10,7 @@ Fresco's large size may seem intimidating, but it need not leave you with a larg
### ProGuard
-You can download Fresco's ProGuard file, [proguard-fresco.pro](https://raw.githubusercontent.com/facebook/fresco/master/proguard-fresco.pro), and add it to your project.
+You can download Fresco's ProGuard file, [proguard-fresco.pro](https://raw.githubusercontent.com/facebook/fresco/master/fbcore/proguard-fresco.pro), and add it to your project.
To enable ProGuard and configure it to use the Fresco configuration, modify your `build.gradle` file to include the lines contained in the `release` section below.
