Mark duplicate import removal suggestion tool only

Author: estebank

src/librustc_resolve/lib.rs

@@ -4932,7 +4932,7 @@ impl<'a> Resolver<'a> {
             Some((directive, _, true)) if should_remove_import && !directive.is_glob() => {
                 // Simple case - remove the entire import. Due to the above match arm, this can
                 // only be a single use so just remove it entirely.
-                err.span_suggestion_hidden(
+                err.tool_only_span_suggestion(
                     directive.use_span_with_attributes,
                     "remove unnecessary import",
                     String::new(),

src/test/ui/double-type-import.stderr

@@ -7,7 +7,6 @@ LL |     use self::bar::X;
    |         ^^^^^^^^^^^^ `X` reimported here
    |
    = note: `X` must be defined only once in the type namespace of this module
-   = help: remove unnecessary import
 
 error: aborting due to previous error
 

src/test/ui/imports/duplicate.stderr

@@ -7,7 +7,6 @@ LL |     use a::foo;
    |         ^^^^^^ `foo` reimported here
    |
    = note: `foo` must be defined only once in the value namespace of this module
-   = help: remove unnecessary import
 
 error[E0659]: `foo` is ambiguous (glob import vs glob import in the same module)
   --> $DIR/duplicate.rs:46:15

src/test/ui/issues/issue-26886.stderr

@@ -7,7 +7,6 @@ LL | use std::sync::Arc;
    |     ^^^^^^^^^^^^^^ `Arc` reimported here
    |
    = note: `Arc` must be defined only once in the type namespace of this module
-   = help: remove unnecessary import
 
 error[E0252]: the name `sync` is defined multiple times
   --> $DIR/issue-26886.rs:4:5
@@ -19,7 +18,6 @@ LL | use std::sync;
    |     ^^^^^^^^^ `sync` reimported here
    |
    = note: `sync` must be defined only once in the type namespace of this module
-   = help: remove unnecessary import
 
 error: aborting due to 2 previous errors
 

src/test/ui/issues/issue-52891.stderr

@@ -7,7 +7,6 @@ LL | use issue_52891::a;
    |     ^^^^^^^^^^^^^^ `a` reimported here
    |
    = note: `a` must be defined only once in the type namespace of this module
-   = help: remove unnecessary import
 
 error[E0252]: the name `a` is defined multiple times
   --> $DIR/issue-52891.rs:14:19
@@ -125,7 +124,6 @@ LL | use issue_52891::n;
    |     ^^^^^^^^^^^^^^ `n` reimported here
    |
    = note: `n` must be defined only once in the type namespace of this module
-   = help: remove unnecessary import
 
 error: aborting due to 10 previous errors
 

src/test/ui/proc-macro/shadow.stderr

@@ -8,7 +8,6 @@ LL | extern crate derive_a;
    | ^^^^^^^^^^^^^^^^^^^^^^ `derive_a` reimported here
    |
    = note: `derive_a` must be defined only once in the type namespace of this module
-   = help: remove unnecessary import
 
 error: aborting due to previous error
 

src/test/ui/resolve/resolve-conflict-import-vs-import.stderr

@@ -7,7 +7,6 @@ LL | use std::mem::transmute;
    |     ^^^^^^^^^^^^^^^^^^^ `transmute` reimported here
    |
    = note: `transmute` must be defined only once in the value namespace of this module
-   = help: remove unnecessary import
 
 error: aborting due to previous error
 

src/test/ui/unresolved/unresolved-extern-mod-suggestion.stderr

@@ -7,7 +7,6 @@ LL | use core;
    |     ^^^^ `core` reimported here
    |
    = note: `core` must be defined only once in the type namespace of this module
-   = help: remove unnecessary import
 
 error: aborting due to previous error
 

src/test/ui/use/use-paths-as-items.stderr

@@ -7,7 +7,6 @@ LL | use std::mem;
    |     ^^^^^^^^ `mem` reimported here
    |
    = note: `mem` must be defined only once in the type namespace of this module
-   = help: remove unnecessary import
 
 error: aborting due to previous error