Update embedded code sample

Author: alexander-yevsyukov

docs/content/docs/validation/01-getting-started/adding-to-build.md

@@ -8,12 +8,8 @@ pluginManagement {
     repositories {
         mavenLocal()
         gradlePluginPortal()
-        maven {
-            url = java.net.URI("https://europe-maven.pkg.dev/spine-event-engine/snapshots")
-        }
-        maven {
-            url = java.net.URI("https://europe-maven.pkg.dev/spine-event-engine/releases")
-        }
+        maven("https://europe-maven.pkg.dev/spine-event-engine/snapshots")
+        maven("https://europe-maven.pkg.dev/spine-event-engine/releases")
     }
 }
 ```
@@ -30,7 +26,6 @@ Choose the setup that matches your project:
 
 Both modes integrate the Validation compiler into the build and add the runtime library.
 
-
 ### Mode 1: standalone via Validation Gradle plugin
 
 Use this mode if you want to run Validation without the rest of Spine.