fix: Fix breaking change by making the previous change Nullable/Optional (#231)

Author: Abhi347

src/main/java/com/spotify/github/v3/checks/CheckRunResponse.java

@@ -80,7 +80,7 @@ public interface CheckRunResponse extends CheckRunBase {
 
   /**
    * Pull Requests where this check is applied.
-   * @return the list of pull requests
+   * @return the optional of list of pull requests
    */
-  List<PartialPullRequestItem> pullRequests();
+  Optional<List<PartialPullRequestItem>> pullRequests();
 }

src/main/java/com/spotify/github/v3/prs/PartialPullRequestItem.java

@@ -34,12 +34,15 @@
 @JsonDeserialize(as = ImmutablePartialPullRequestItem.class)
 public interface PartialPullRequestItem extends CloseTracking {
   /** ID. */
+  @Nullable
   Long id();
 
   /** URL. */
+  @Nullable
   URI url();
 
   /** Number. */
+  @Nullable
   Long number();
 
   /** Head reference. */