Remove redundant "Correct Answer: X" heading from the review panel

Now that the explanation panel is docked inside the correct choice's
own green card, the heading was redundant with the badge/border color
already conveying it's the correct answer.

scripts/ui/question_player.gd

@@ -70,7 +70,6 @@ var lead_label: Label
 var explanation_label: RichTextLabel
 var references_container: VBoxContainer
 var correct_review_panel: PanelContainer
-var correct_answer_heading: Label
 var teaching_cards: HFlowContainer
 var review_followups_section: VBoxContainer
 var review_followups_content: VBoxContainer
@@ -598,10 +597,6 @@ func _build_answer_review_ui() -> void:
 	review_content.add_theme_constant_override("separation", 10)
 	review_margin.add_child(review_content)
 
-	correct_answer_heading = Label.new()
-	_set_scaled_label(correct_answer_heading, 17, Brand.SUCCESS)
-	review_content.add_child(correct_answer_heading)
-
 	explanation_label = RichTextLabel.new()
 	explanation_label.bbcode_enabled = true
 	explanation_label.fit_content = true
@@ -1521,7 +1516,6 @@ func _show_explanation() -> void:
 	var correct_id := str(question.get("correct_choice_id", ""))
 	_dock_correct_review_panel(correct_id)
 	correct_review_panel.visible = true
-	correct_answer_heading.text = "Correct Answer: %s" % _display_label_for_choice_id(correct_id)
 	var choices := _get_presented_choices()
 	for index in range(choices.size()):
 		var choice: Dictionary = choices[index]