Bump minimum common Java requirement to 17

This is now the third-oldest LTS version, supporting anything older is not worth the build headache and outdated dependencies anymore.

Author: jpenilla

gradle/build-logic/src/main/kotlin/minimotd.base-conventions.gradle.kts

@@ -11,9 +11,9 @@ version = (version as String)
 
 indra {
   javaVersions {
-    testWith(11, 17, 21)
-    target(11)
+    target(17)
     minimumToolchain(21)
+    testWith(17, 21, 25)
   }
   github(Constants.GITHUB_USER, Constants.GITHUB_REPO)
   mitLicense()