[FIR] Remove the TODO from FirModifierChecker.kt

Pasha said we can delete it.

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirModifierChecker.kt

@@ -183,7 +183,6 @@ object FirModifierChecker : FirBasicDeclarationChecker() {
             val set = map[modifierToken] ?: emptySet()
             val checkResult = if (factory == FirErrors.WRONG_MODIFIER_TARGET) {
                 actualTargets.none { it in set } ||
-                        // TODO: Implement some generic feature-checking mechanism
                         (modifierToken == DATA_KEYWORD
                                 && actualTargets.contains(KotlinTarget.STANDALONE_OBJECT)
                                 && !context.languageVersionSettings.supportsFeature(LanguageFeature.DataObjects))