Use latest DV plugin version in docs

Author: bigdaz

docs/setup-gradle.md

@@ -915,7 +915,7 @@ Here's an example using the env vars:
         DEVELOCITY_INJECTION_ENABLED: true
         DEVELOCITY_URL: https://develocity.your-server.com
         DEVELOCITY_ENFORCE_URL: true
-        DEVELOCITY_PLUGIN_VERSION: "3.18.1"
+        DEVELOCITY_PLUGIN_VERSION: "3.19"
         DEVELOCITY_CCUD_PLUGIN_VERSION: "2.0.2"
 ```