return unmodifiable list

Author: Joe

src/main/java/org/kohsuke/github/GHCheckRun.java

@@ -117,7 +117,7 @@ public List<GHPullRequest> getPullRequests() throws IOException {
             for (GHPullRequest singlePull : pullRequests) {
                 singlePull.refresh();
             }
-            return Arrays.asList(pullRequests);
+            return Collections.unmodifiableList(Arrays.asList(pullRequests));
         }
         return Collections.emptyList();
     }

src/main/java/org/kohsuke/github/GHCheckSuite.java

@@ -165,7 +165,7 @@ public List<GHPullRequest> getPullRequests() throws IOException {
             for (GHPullRequest singlePull : pullRequests) {
                 singlePull.refresh();
             }
-            return Arrays.asList(pullRequests);
+            return Collections.unmodifiableList(Arrays.asList(pullRequests));
         }
         return Collections.emptyList();
     }