show apns expiration banner in UI for free tier (#40936)

**Related issue:** Resolves #39184

show apns expiration banner for the free tier in the UI. Before it was
limited to show only for premium tier.

- [x] Changes file added for user-visible changes in `changes/`,
`orbit/changes/` or `ee/fleetd-chrome/changes`.
- [x] QA'd all new/changed functionality manually

---------

Co-authored-by: Nico <32375741+nulmete@users.noreply.github.com>

changes/issue-39184-apns-banner-fix

@@ -0,0 +1 @@
+- Added APNs expiry banner in the UI for fleet free tier.

frontend/components/MainContent/MainContent.tsx

@@ -57,10 +57,12 @@ const MainContent = ({
 
     // the order of these checks is important. This is the priority order
     // for showing banners and only one banner is shown at a time.
-    if (isPremiumTier) {
-      if (isApplePnsExpired || willApplePnsExpire) {
-        banner = <ApplePNCertRenewalMessage expired={isApplePnsExpired} />;
-      } else if (isAndroidEnterpriseDeleted) {
+    if (isApplePnsExpired || willApplePnsExpire) {
+      // APNs expiration banner will show for either premium or free tiers
+      // but all other banners are only for premium tiers
+      banner = <ApplePNCertRenewalMessage expired={isApplePnsExpired} />;
+    } else if (isPremiumTier) {
+      if (isAndroidEnterpriseDeleted) {
         banner = <AndroidEnterpriseDeletedMessage />;
       } else if (isAppleBmExpired || willAppleBmExpire) {
         banner = <AppleBMRenewalMessage expired={isAppleBmExpired} />;