Fix invalid check-cfg Cargo feature diagnostic help

Author: Urgau

compiler/rustc_lint/src/context.rs

@@ -804,8 +804,6 @@ pub trait LintContext {
                                 db.span_suggestion(value_span, "there is a expected value with a similar name", format!("\"{best_match}\""), Applicability::MaybeIncorrect);
 
                             }
-                        } else if name == sym::feature && is_from_cargo {
-                            db.help(format!("consider defining `{name}` as feature in `Cargo.toml`"));
                         } else if let &[first_possibility] = &possibilities[..] {
                             db.span_suggestion(name_span.shrink_to_hi(), "specify a config value", format!(" = \"{first_possibility}\""), Applicability::MaybeIncorrect);
                         }

tests/ui/check-cfg/cargo-feature.some.stderr

@@ -13,10 +13,9 @@ warning: unexpected `cfg` condition value: (none)
   --> $DIR/cargo-feature.rs:18:7
    |
 LL | #[cfg(feature)]
-   |       ^^^^^^^
+   |       ^^^^^^^- help: specify a config value: `= "bitcode"`
    |
    = note: expected values for `feature` are: `bitcode`
-   = help: consider defining `feature` as feature in `Cargo.toml`
    = note: see <https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#check-cfg> for more information about checking conditional configuration
 
 warning: unexpected `cfg` condition name: `tokio_unstable`