Mark "unused binding" suggestion as maybe incorrect

Ignoring unused bindings should be a determination made by a human, `rustfix` shouldn't auto-apply the suggested change.

Fix #54196.

Author: estebank

compiler/rustc_passes/src/errors.rs

@@ -1739,7 +1739,7 @@ pub struct UnusedVariableTryPrefix {
 
 #[derive(Subdiagnostic)]
 pub enum UnusedVariableSugg {
-    #[multipart_suggestion(passes_suggestion, applicability = "machine-applicable")]
+    #[multipart_suggestion(passes_suggestion, applicability = "maybe-incorrect")]
     TryPrefixSugg {
         #[suggestion_part(code = "_{name}")]
         spans: Vec<Span>,
@@ -1778,7 +1778,7 @@ pub struct UnusedVarTryIgnore {
 }
 
 #[derive(Subdiagnostic)]
-#[multipart_suggestion(passes_suggestion, applicability = "machine-applicable")]
+#[multipart_suggestion(passes_suggestion, applicability = "maybe-incorrect")]
 pub struct UnusedVarTryIgnoreSugg {
     #[suggestion_part(code = "{name}: _")]
     pub shorthands: Vec<Span>,