Fix clippy errors.

src/parser/comment.rs

@@ -106,7 +106,6 @@ mod tests {
     use super::*;
     use crate::context::bind_context;
     use crate::context::Context;
-    use crate::context::ContextElement;
     use crate::context::GlobalSettings;
     use crate::context::List;
 

src/parser/headline.rs

@@ -77,9 +77,9 @@ fn _heading<'b, 'g, 'r, 's>(
         // If the section has a planning then the timestamp values are copied to the heading.
         if let DocumentElement::Section(inner_section) = &section {
             if let Some(Element::Planning(planning)) = inner_section.children.first() {
-                scheduled = planning.scheduled.clone();
-                deadline = planning.deadline.clone();
-                closed = planning.closed.clone();
+                scheduled.clone_from(&planning.scheduled);
+                deadline.clone_from(&planning.deadline);
+                closed.clone_from(&planning.closed);
             }
         }
         children.insert(0, section);

src/parser/keyword.rs

@@ -224,7 +224,6 @@ mod tests {
     use test::Bencher;
 
     use super::*;
-    use crate::parser::OrgSource;
 
     #[bench]
     fn bench_affiliated_keyword(b: &mut Bencher) {

src/parser/radio_link.rs

@@ -175,9 +175,7 @@ pub(crate) trait RematchObject<'x> {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::context::Context;
     use crate::context::GlobalSettings;
-    use crate::context::List;
     use crate::parser::element_parser::element;
     use crate::types::Bold;
     use crate::types::Element;