fix a bad error message for relative paths are not supported in visibilities error

Author: TaKO8Ki

compiler/rustc_resolve/src/diagnostics.rs

@@ -632,7 +632,7 @@ impl<'a> Resolver<'a> {
             VisResolutionError::Relative2018(span, path) => {
                 let mut err = self.session.struct_span_err(
                     span,
-                    "relative paths are not supported in visibilities on 2018 edition",
+                    "relative paths are not supported in visibilities in 2018 edition or later",
                 );
                 err.span_suggestion(
                     path.span,

src/test/ui/privacy/restricted/relative-2018.rs

@@ -7,7 +7,7 @@ mod m {
     pub(in ::core) struct S4;
     //~^ ERROR visibilities can only be restricted to ancestor modules
     pub(in a::b) struct S5;
-    //~^ ERROR relative paths are not supported in visibilities on 2018 edition
+    //~^ ERROR relative paths are not supported in visibilities in 2018 edition or later
 }
 
 fn main() {}

src/test/ui/privacy/restricted/relative-2018.stderr

@@ -4,7 +4,7 @@ error[E0742]: visibilities can only be restricted to ancestor modules
 LL |     pub(in ::core) struct S4;
    |            ^^^^^^
 
-error: relative paths are not supported in visibilities on 2018 edition
+error: relative paths are not supported in visibilities in 2018 edition or later
   --> $DIR/relative-2018.rs:9:12
    |
 LL |     pub(in a::b) struct S5;