Remove redundant imports

These became warnings in a recent nightly.

The TryFrom/TryInto imports were missed in
4089891f6c, but the rest are truly
redundant.

parsers/src/vcard.rs

@@ -95,7 +95,6 @@ impl IqResultPayload for VCard {}
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::Element;
     use base64::Engine;
     use std::str::FromStr;