Elide lifetimes where possible after rustup (#34824)

The new version of rust allows us to elide some lifetimes and clippy is
now complaining about this. This change elides them where possible and
removes the clippy exceptions.

Fixes #34804.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>

components/script/dom/bindings/callback.rs

@@ -216,7 +216,7 @@ impl<T: DomObject> ThisReflector for T {
     }
 }
 
-impl<'a> ThisReflector for HandleObject<'a> {
+impl ThisReflector for HandleObject<'_> {
     fn jsobject(&self) -> *mut JSObject {
         self.get()
     }

components/script/dom/bindings/root.rs

@@ -260,7 +260,7 @@ impl<'a> ThreadLocalStackRoots<'a> {
     }
 }
 
-impl<'a> Drop for ThreadLocalStackRoots<'a> {
+impl Drop for ThreadLocalStackRoots<'_> {
     fn drop(&mut self) {
         STACK_ROOTS.with(|r| r.set(None));
     }
@@ -698,7 +698,7 @@ impl<T: DomObject> PartialEq for MutNullableDom<T> {
     }
 }
 
-impl<'a, T: DomObject> PartialEq<Option<&'a T>> for MutNullableDom<T> {
+impl<T: DomObject> PartialEq<Option<&T>> for MutNullableDom<T> {
     fn eq(&self, other: &Option<&T>) -> bool {
         unsafe { *self.ptr.get() == other.map(Dom::from_ref) }
     }

components/script/dom/bindings/str.rs

@@ -356,7 +356,7 @@ impl From<String> for DOMString {
     }
 }
 
-impl<'a> From<&'a str> for DOMString {
+impl From<&str> for DOMString {
     fn from(contents: &str) -> DOMString {
         DOMString::from(String::from(contents))
     }