chore(lean): Fix for unused variable linter

Author: abentkamp

rust-engine/src/backends/lean.rs

@@ -789,7 +789,7 @@ set_option linter.unusedVariables false
                 Literal::Float {
                     value,
                     negative,
-                    kind,
+                    kind: _,
                 } => format!("{}{value}", if *negative { "-" } else { "" }),
             }]
         }