remove remaining todo flags

runtime/Dart/lib/src/atn/src/parser_atn_simulator.dart

@@ -626,7 +626,7 @@ class ParserATNSimulator extends ATNSimulator {
   }
 
   void predicateDFAState(DFAState dfaState, DecisionState? decisionState) {
-    // Todo: this if was added due to a possuble null pointer error
+    // Todo: this if was added due to a possible null pointer error
     if (decisionState == null) return;
 
     // We need to test all predicates, even in DFA states that

runtime/Dart/lib/src/parser.dart

@@ -59,7 +59,7 @@ abstract class Parser extends Recognizer<ParserATNSimulator> {
   /// later call to {@link #setTrace}{@code (false)}. The listener itself is
   /// implemented as a parser listener so this field is not directly used by
   /// other parser methods.
-  TraceListener? _tracer; // Todo: this is nullable and nothing can change this
+  TraceListener? _tracer;
 
   /// The list of [ParseTreeListener] listeners registered to receive
   /// events during the parse.
@@ -236,7 +236,7 @@ abstract class Parser extends Recognizer<ParserATNSimulator> {
   ///
   /// @throws NullPointerException if {@code} listener is null
   void addParseListener(
-    ParseTreeListener listener, //Todo: never make it null
+    ParseTreeListener listener,
   ) {
     _parseListeners ??= [];
 

runtime/Dart/lib/src/parser_rule_context.dart

@@ -43,7 +43,7 @@ class ParserRuleContext extends RuleContext {
   /// Get the initial/final token in this context.
   /// Note that the range from start to stop is inclusive, so for rules that do not consume anything
   /// (for example, zero length or error productions) this token may exceed stop.
-  Token? start, stop; // Todo: keep an eye on this late
+  Token? start, stop;
 
   /// The exception that forced this rule to return. If the rule successfully
   /// completed, this is null.

runtime/Dart/lib/src/prediction_context.dart

@@ -828,8 +828,7 @@ class ArrayPredictionContext extends PredictionContext {
   /// Parent can be null only if full ctx mode and we make an array
   ///  from {@link #EMPTY} and non-empty. We merge {@link #EMPTY} by using null parent and
   ///  returnState == {@link #EMPTY_RETURN_STATE}.
-  List<PredictionContext?>
-      parents; // Todo: this generic should be null this wont change
+  List<PredictionContext?> parents;
 
   /// Sorted for merge, no duplicates; if present,
   ///  {@link #EMPTY_RETURN_STATE} is always last.