Add explicit error annotations to test.

This commit adds explicit error annotations to tests after rebasing
which is now required.

Author: davidtwco

src/test/ui/issue-54943.rs

@@ -4,4 +4,5 @@ fn main<'a>() {
     return;
 
     let x = foo::<&'a u32>();
+    //~^ ERROR the type `&'a u32` does not fulfill the required lifetime [E0477]
 }

src/test/ui/issue-55511.nll.stderr

@@ -3,7 +3,7 @@ error[E0597]: `a` does not live long enough
    |
 LL |     let b = Some(Cell::new(&a));
    |                            ^^ borrowed value does not live long enough
-LL |     match b {
+...
 LL |         <() as Foo<'static>>::C => { }
    |         ----------------------- type annotation requires that `a` is borrowed for `'static`
 ...

src/test/ui/issue-55511.rs

@@ -11,6 +11,7 @@ impl<'a, T> Foo<'a> for T {
 fn main() {
     let a = 22;
     let b = Some(Cell::new(&a));
+    //~^ ERROR `a` does not live long enough [E0597]
     match b {
         <() as Foo<'static>>::C => { }
         _ => { }