Fixed clippy warnings.

src/common.rs

@@ -223,12 +223,12 @@ impl<T, H> Drop for Slice<T, H> {
 
 impl<T, H> SliceVec<T, H> {
     /// Create an immutable iterator over the elements of the vector.
-    pub fn iter<'a>(&'a self) -> slice::Iter<'a, T> {
+    pub fn iter(&self) -> slice::Iter<'_, T> {
         self.slice.iter()
     }
 
     /// Create an mutable iterator over the elements of the vector.
-    pub fn iter_mut<'a>(&'a mut self) -> slice::IterMut<'a, T> {
+    pub fn iter_mut(&mut self) -> slice::IterMut<'_, T> {
         self.slice.iter_mut()
     }
 }

src/region.rs

@@ -92,7 +92,7 @@ impl Arena {
     /// Return a fresh generation token for the arena.
     ///
     /// If a generation of objects is currently live, an error is returned instead.
-    pub fn generation_token<'a>(&'a self) -> Result<ArenaToken<'a>, ArenaError> {
+    pub fn generation_token(&self) -> Result<ArenaToken<'_>, ArenaError> {
         if self.locked.get() {
             Err(ArenaError::AlreadyLocked)
         } else {