Avoid unhelpful suggestion when crate name is invalid

compiler/rustc_session/messages.ftl

@@ -57,7 +57,6 @@ session_int_literal_too_large = integer literal is too large
     .note = value exceeds limit of `{$limit}`
 
 session_invalid_character_in_crate_name = invalid character {$character} in crate name: `{$crate_name}`
-    .help = you can either pass `--crate-name` on the command line or add `#![crate_name = "…"]` to set the crate name
 
 session_invalid_float_literal_suffix = invalid suffix `{$suffix}` for float literal
     .label = invalid suffix `{$suffix}`

compiler/rustc_session/src/errors.rs

@@ -238,8 +238,6 @@ pub(crate) struct InvalidCharacterInCrateName {
     pub(crate) span: Option<Span>,
     pub(crate) character: char,
     pub(crate) crate_name: Symbol,
-    #[help]
-    pub(crate) help: Option<()>,
 }
 
 #[derive(Subdiagnostic)]

compiler/rustc_session/src/output.rs

@@ -69,7 +69,6 @@ pub fn validate_crate_name(sess: &Session, crate_name: Symbol, span: Option<Span
             span,
             character: c,
             crate_name,
-            help: span.is_none().then_some(()),
         }));
     }
 

tests/ui/compile-flags/invalid/need-crate-arg-ignore-tidy$x.stderr

@@ -1,6 +1,4 @@
 error: invalid character '$' in crate name: `need_crate_arg_ignore_tidy$x`
-   |
-   = help: you can either pass `--crate-name` on the command line or add `#![crate_name = "…"]` to set the crate name
 
 error: aborting due to 1 previous error