Update the expected stderr for coerce-issue-49593-box-never.

This test's expected stderr now includes a count of the number of types
that implment `Error`. This PR introduces two new types, so increment
the number by two.

Author: sunfishcode

src/test/ui/coercion/coerce-issue-49593-box-never.nofallback.stderr

@@ -13,7 +13,7 @@ LL |     /* *mut $0 is coerced to Box<dyn Error> here */ Box::<_ /* ! */>::new(x
              BorrowError
              BorrowMutError
              Box<T>
-           and 43 others
+           and 45 others
    = note: required for the cast to the object type `dyn std::error::Error`
 
 error[E0277]: the trait bound `(): std::error::Error` is not satisfied
@@ -31,7 +31,7 @@ LL |     /* *mut $0 is coerced to *mut Error here */ raw_ptr_box::<_ /* ! */>(x)
              BorrowError
              BorrowMutError
              Box<T>
-           and 43 others
+           and 45 others
    = note: required for the cast to the object type `(dyn std::error::Error + 'static)`
 
 error: aborting due to 2 previous errors