Update build.gradle

build.gradle

             name = "GitHubPackages"
             url = uri("https://maven.pkg.github.com/dmdirc/util")
             credentials {
-                username = project.findProperty("gpr.user") ?: System.getenv("USERNAME")
-                password = project.findProperty("gpr.key") ?: System.getenv("PASSWORD")
+                username = findProperty("GITHUB_USERNAME")
+                password = findProperty("GITHUB_API_TOKEN")
             }
         }
     }