feat: add unit title to pluginslot (#1383)

src/courseware/course/sequence/Unit/__snapshots__/index.test.jsx.snap

@@ -31,6 +31,7 @@ exports[`Unit component output snapshot: not bookmarked, do not show content 1`]
     <UnitTitleSlot
       courseId="test-course-id"
       unitId="test-props-id"
+      unitTitle="unit-title"
     />
   </div>
   <h2

src/courseware/course/sequence/Unit/index.jsx

@@ -43,7 +43,7 @@ const Unit = ({
     <div className="unit">
       <div className="mb-0">
         <h3 className="h3">{unit.title}</h3>
-        <UnitTitleSlot courseId={courseId} unitId={id} />
+        <UnitTitleSlot courseId={courseId} unitId={id} unitTitle={unit.title} />
       </div>
       <h2 className="sr-only">{formatMessage(messages.headerPlaceholder)}</h2>
       <BookmarkButton