Normalize wording of privacy access labels

src/test/ui/error-codes/E0451.stderr

@@ -2,13 +2,13 @@ error[E0451]: field `b` of struct `bar::Foo` is private
   --> $DIR/E0451.rs:14:21
    |
 LL |     let bar::Foo{a, b} = foo;
-   |                     ^ field `b` is private
+   |                     ^ private field
 
 error[E0451]: field `b` of struct `bar::Foo` is private
   --> $DIR/E0451.rs:18:29
    |
 LL |     let f = bar::Foo{ a: 0, b: 0 };
-   |                             ^^^^ field `b` is private
+   |                             ^^^^ private field
 
 error: aborting due to 2 previous errors
 

src/test/ui/error-codes/E0603.stderr

@@ -2,7 +2,7 @@ error[E0603]: constant `PRIVATE` is private
   --> $DIR/E0603.rs:6:17
    |
 LL |     SomeModule::PRIVATE;
-   |                 ^^^^^^^ this constant is private
+   |                 ^^^^^^^ private constant
    |
 note: the constant `PRIVATE` is defined here
   --> $DIR/E0603.rs:2:5

src/test/ui/error-codes/E0624.stderr

@@ -2,7 +2,7 @@ error[E0624]: associated function `method` is private
   --> $DIR/E0624.rs:11:9
    |
 LL |     foo.method();
-   |         ^^^^^^
+   |         ^^^^^^ private associated function
 
 error: aborting due to previous error