fix: first section celebration

Fix the first section celebration modal showing logic.

On Nutmeg+ it's shown only after the page reload or after going directly
to the second section from the course home. Going through the course
with the Next/Previous buttons has no effect (which worked on Maple).

Notes:
- the weekly goal has the same showing logic, but I assume that is
correct behavior so no changes are added for it in this commit.
- showing a celebration modal for the first section completion when
going directly to the first unit of the second section seems to be a bug
(reproduces on Maple too)

src/courseware/course/Course.jsx

@@ -1,4 +1,4 @@
-import React, { useState } from 'react';
+import React, { useEffect, useState } from 'react';
 import PropTypes from 'prop-types';
 import { Helmet } from 'react-helmet';
 import { useDispatch } from 'react-redux';
@@ -43,10 +43,8 @@ const Course = ({
 
   // Below the tabs, above the breadcrumbs alerts (appearing in the order listed here)
   const dispatch = useDispatch();
-  const celebrateFirstSection = celebrations && celebrations.firstSection;
-  const [firstSectionCelebrationOpen, setFirstSectionCelebrationOpen] = useState(
-    shouldCelebrateOnSectionLoad(courseId, sequenceId, celebrateFirstSection, dispatch, celebrations),
-  );
+
+  const [firstSectionCelebrationOpen, setFirstSectionCelebrationOpen] = useState(false);
   // If streakLengthToCelebrate is populated, that modal takes precedence. Wait til the next load to display
   // the weekly goal celebration modal.
   const [weeklyGoalCelebrationOpen, setWeeklyGoalCelebrationOpen] = useState(
@@ -68,6 +66,17 @@ const Course = ({
     }
   }
 
+  useEffect(() => {
+    const celebrateFirstSection = celebrations && celebrations.firstSection;
+    setFirstSectionCelebrationOpen(shouldCelebrateOnSectionLoad(
+      courseId,
+      sequenceId,
+      celebrateFirstSection,
+      dispatch,
+      celebrations,
+    ));
+  }, [sequenceId]);
+
   return (
     <SidebarProvider courseId={courseId} unitId={unitId}>
       <Helmet>