Add missing import.

app.py

@@ -17,6 +17,7 @@ from src.about import (  # ⬅️ split to insert the tabs right after the headi
     CITATION_BUTTON_LABEL,
     CITATION_BUTTON_TEXT,
     EVALUATION_QUEUE_TEXT,
+    WHAT_IS_F1_HTML_BOTTOM_B,
     WHAT_IS_F1_HTML_TOP,
 )
 from src.datamodel.data import F1Data