unread tests: Fix bogus flag name 'star' to 'starred'

This wasn't actually the name of any flag.

We haven't previously written down in our API types what the set
of expected flags actually is.  When we do, Flow starts pointing
out this discrepancy; so fix it first.

Author: gnprice

src/unread/__tests__/unreadHuddlesReducer-test.js

@@ -191,7 +191,7 @@ describe('unreadHuddlesReducer', () => {
         all: false,
         allMessages: eg.makeMessagesState([]),
         messages: [1, 2, 3],
-        flag: 'star',
+        flag: 'starred',
         op: 'add',
       };
 

src/unread/__tests__/unreadMentionsReducer-test.js

@@ -97,7 +97,7 @@ describe('unreadMentionsReducer', () => {
         all: false,
         allMessages: Immutable.Map(),
         messages: [1, 2, 3],
-        flag: 'star',
+        flag: 'starred',
         op: 'add',
       };
 

src/unread/__tests__/unreadModel-test.js

@@ -294,7 +294,7 @@ describe('stream substate', () => {
     });
 
     test('when operation is "add" but flag is not "read" do not mutate state', () => {
-      const action = mkAction({ messages: [1, 2, 3], flag: 'star' });
+      const action = mkAction({ messages: [1, 2, 3], flag: 'starred' });
       expect(reducer(initialState, action, eg.plusReduxState)).toBe(initialState);
     });
 

src/unread/__tests__/unreadPmsReducer-test.js

@@ -201,7 +201,7 @@ describe('unreadPmsReducer', () => {
         all: false,
         allMessages: eg.makeMessagesState([]),
         messages: [1, 2, 3],
-        flag: 'star',
+        flag: 'starred',
         op: 'add',
       };