MINOR: Downgrade log level for conflicting Connect plugin aliases (#14081)

Reviewers: Greg Harris <greg.harris@aiven.io>

connect/runtime/src/main/java/org/apache/kafka/connect/runtime/isolation/PluginUtils.java

@@ -408,7 +408,7 @@ public class PluginUtils {
             if (classNames.size() == 1) {
                 aliases.put(alias, classNames.stream().findAny().get());
             } else {
-                log.warn("Ignoring ambiguous alias '{}' since it refers to multiple distinct plugins {}", alias, classNames);
+                log.debug("Ignoring ambiguous alias '{}' since it refers to multiple distinct plugins {}", alias, classNames);
             }
         }
         return aliases;