Resolve some needless_lifetimes clippy lints

    warning: the following explicit lifetimes could be elided: 'a
       --> src/bytes.rs:106:6
        |
    106 | impl<'a> Default for &'a Bytes {
        |      ^^               ^^
        |
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_lifetimes
        = note: `-W clippy::needless-lifetimes` implied by `-W clippy::all`
        = help: to override `-W clippy::all` add `#[allow(clippy::needless_lifetimes)]`
    help: elide the lifetimes
        |
    106 - impl<'a> Default for &'a Bytes {
    106 + impl Default for &Bytes {
        |

    warning: the following explicit lifetimes could be elided: 'a
       --> src/ser.rs:102:6
        |
    102 | impl<'a, T> Serialize for &'a T
        |      ^^                    ^^
        |
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_lifetimes
    help: elide the lifetimes
        |
    102 - impl<'a, T> Serialize for &'a T
    102 + impl<T> Serialize for &T
        |

Author: dtolnay

src/bytes.rs

@@ -103,7 +103,7 @@ impl From<Box<[u8]>> for Box<Bytes> {
     }
 }
 
-impl<'a> Default for &'a Bytes {
+impl Default for &Bytes {
     fn default() -> Self {
         Bytes::new(&[])
     }

src/ser.rs

@@ -99,7 +99,7 @@ impl<'a> Serialize for Cow<'a, Bytes> {
     }
 }
 
-impl<'a, T> Serialize for &'a T
+impl<T> Serialize for &T
 where
     T: ?Sized + Serialize,
 {