xmpp-parsers: Stop reexporting extra symbols

Let’s continue reexporting jid and minidom, but not their inner pub
items, users of this crate can go one level deeper if they need that.

Only xso::error::Error is still useful to reexport, as this is part of
the public API of all of our parsers.

parsers/src/sm.rs

@@ -146,7 +146,7 @@ pub struct StreamManagement;
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::Element;
+    use minidom::Element;
 
     #[cfg(target_pointer_width = "32")]
     #[test]