fix(): add missing category to AI

Author: fdelbrayelle

src/main/java/io/kestra/plugin/perplexity/package-info.java

@@ -0,0 +1,8 @@
+@PluginSubGroup(
+    title = "Perplexity plugin",
+    description = "A plugin to use Perplexity.",
+    categories = PluginSubGroup.PluginCategory.AI
+)
+package io.kestra.plugin.perplexity;
+
+import io.kestra.core.models.annotations.PluginSubGroup;