Resolve needless_lifetimes clippy lint

    warning: the following explicit lifetimes could be elided: 'a
      --> src/unindent.rs:83:6
       |
    83 | impl<'a, T: ?Sized + Unindent> Unindent for &'a T {
       |      ^^                                      ^^
       |
       = 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
       |
    83 - impl<'a, T: ?Sized + Unindent> Unindent for &'a T {
    83 + impl<T: ?Sized + Unindent> Unindent for &T {
       |

Author: dtolnay

src/lib.rs

@@ -127,7 +127,6 @@
     clippy::from_iter_instead_of_collect,
     clippy::module_name_repetitions,
     clippy::needless_doctest_main,
-    clippy::needless_lifetimes,
     clippy::needless_pass_by_value,
     clippy::trivially_copy_pass_by_ref,
     clippy::type_complexity

src/unindent.rs

@@ -80,7 +80,7 @@ impl Unindent for [u8] {
     }
 }
 
-impl<'a, T: ?Sized + Unindent> Unindent for &'a T {
+impl<T: ?Sized + Unindent> Unindent for &T {
     type Output = T::Output;
 
     fn unindent(&self) -> Self::Output {

unindent/src/lib.rs

@@ -51,7 +51,6 @@
     clippy::module_name_repetitions,
     clippy::must_use_candidate,
     clippy::needless_doctest_main,
-    clippy::needless_lifetimes,
     clippy::trivially_copy_pass_by_ref,
     clippy::type_complexity
 )]