Revert "feat(generate): warn about unreachable variables (#4567)"

This reverts commit 25c601bd2f.

Reason: Too many false positives.

crates/generate/src/parse_grammar.rs

@@ -247,7 +247,6 @@ pub(crate) fn parse_grammar(input: &str) -> ParseGrammarResult<InputGrammar> {
                 &mut in_progress,
             )
         {
-            eprintln!("Warning: unused variable {name:?}");
             grammar_json.conflicts.retain(|r| !r.contains(name));
             grammar_json.supertypes.retain(|r| r != name);
             grammar_json.inline.retain(|r| r != name);