chore: Deduplicate tags

Signed-off-by: Awiteb <a@4rs.nl>

src/nostr_utils/traits.rs

@@ -102,6 +102,7 @@ impl EventBuilder {
                 euc: None,
                 maintainers,
             })?
+            .dedup_tags()
             .tags(labels.into_iter().map(Tag::hashtag)),
         )
     }