[cfe] Remove obsolete TODOs

Change-Id: I2e0d09850a8aeffdb1816cf81ae5f4595b1cfa02
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/397780
Reviewed-by: Johnni Winther <johnniwinther@google.com>
Commit-Queue: Chloe Stefantsova <cstefantsova@google.com>

pkg/kernel/lib/type_algebra.dart

@@ -1846,7 +1846,6 @@ class _PrimitiveTypeVerifier implements DartTypeVisitor<bool> {
 ///
 /// Some types are nullable even without the application of the nullable type
 /// constructor at the top level, for example, Null or FutureOr<int?>.
-// TODO(cstefantsova): Remove [coreTypes] parameter when NullType is landed.
 DartType unwrapNullabilityConstructor(DartType type) {
   return type.accept(const _NullabilityConstructorUnwrapper());
 }
@@ -1855,8 +1854,6 @@ DartType unwrapNullabilityConstructor(DartType type) {
 ///
 /// Implementing the function as a visitor makes the necessity of supporting a
 /// new implementation of [DartType] visible at compile time.
-// TODO(cstefantsova): Remove CoreTypes as the second argument when NullType is
-// landed.
 class _NullabilityConstructorUnwrapper implements DartTypeVisitor<DartType> {
   const _NullabilityConstructorUnwrapper();