Do not base cache expiry on subscription expiry date (#1150)

Please review the release process for BrowserServicesKit
[here](https://app.asana.com/0/1200194497630846/1200837094583426).

**Required**:

Task/Issue URL:
https://app.asana.com/0/1201037661562251/1209111606760738/f
iOS PR: /will follow in internal build - not impacted/
macOS PR: duckduckgo/macos-browser#3714
What kind of version bump will this require?: Hotfix

**Optional**:

CC: @federicocappelli 

**Description**:
In specific conditions we may cause an endless loop of remote API calls
to fetch the subscription.

**Steps to test this PR**:
(macOS only)
1. Have an expired subscription in the app
2. Ensure that `isLaunchedROW` or `isLaunchedROWOverride` feature flag
is enabled in privacy config.
3. Open Settings tab
4. From sidebar open "Privacy Pro"
5. Check network calls: only a single remote call should be made to GET
subscription from subscriptions BE endpoint

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**OS Testing**:
* [ ] macOS

---
###### Internal references:
[Software Engineering
Expectations](https://app.asana.com/0/59792373528535/199064865822552)
[Technical Design
Template](https://app.asana.com/0/59792373528535/184709971311943)

Sources/Subscription/API/SubscriptionEndpointService.swift

@@ -100,10 +100,7 @@ public struct DefaultSubscriptionEndpointService: SubscriptionEndpointService {
 
         let cachedSubscription: Subscription? = subscriptionCache.get()
         if subscription != cachedSubscription {
-            let defaultExpiryDate = Date().addingTimeInterval(subscriptionCache.settings.defaultExpirationInterval)
-            let expiryDate = min(defaultExpiryDate, subscription.expiresOrRenewsAt)
-
-            subscriptionCache.set(subscription, expires: expiryDate)
+            subscriptionCache.set(subscription)
             NotificationCenter.default.post(name: .subscriptionDidChange, object: self, userInfo: [UserDefaultsCacheKey.subscription: subscription])
         }
     }