Raise SystemExit(0) quietly, instead of ValueErrors or Exception errors to prevent failed GitHub Jobs (#1735)

This is so that we don't see the failed jobs whenever a PR is not
cherry-pickable. Instead, it quitely exits with code 0. So no failed
jobs will occur.
diff --git a/actions/cherry-picker/functions.py b/actions/cherry-picker/functions.py
index 000143f..bad2ee4 100644
--- a/actions/cherry-picker/functions.py
+++ b/actions/cherry-picker/functions.py
@@ -16,18 +16,25 @@
         if (event["actor"]["login"] in actor_name) and (event["commit_id"] != None) and (commit_id == None) and (event["event"] == action_event):
             commit_id = event["commit_id"]
         elif (event["actor"]["login"] in actor_name) and (event["commit_id"] != None) and (commit_id != None) and (event["event"] == action_event):
-            raise Exception(f'PR#{pr_number} has multiple commits made by {actor_name}')
-    if commit_id == None: raise Exception(f'PR#{pr_number} has NO commit made by {actor_name}')
+            print(f'PR#{pr_number} has multiple commits made by {actor_name}')
+            raise SystemExit(0)
+    if commit_id == None:
+        print(f'PR#{pr_number} has NO commit made by {actor_name}')
+        raise SystemExit(0)
     return commit_id
 
 def get_reviewers(pr_number, api_repo_name, issues_data):
     if "pull_request" not in issues_data: return []
     r = requests.get(f'https://api.github.com/repos/{api_repo_name}/pulls/{pr_number}/reviews', headers=headers)
-    if len(r.json()) == 0: raise Exception(f"PR#{pr_number} has no approver at all.")
+    if len(r.json()) == 0:
+        print(f"PR#{pr_number} has no approver at all.")
+        raise SystemExit(0)
     approvers_list = []
     for review in r.json():
         if review["state"] == "APPROVED": approvers_list.append(review["user"]["login"])
-    if len(approvers_list) == 0: raise Exception(f"PR#{pr_number} has no approval from the approver(s).")
+    if len(approvers_list) == 0:
+        print(f"PR#{pr_number} has no approval from the approver(s).")
+        raise SystemExit(0)
     return approvers_list
 
 def extract_release_numbers_data(pr_number, api_repo_name):
diff --git a/actions/cherry-picker/index.py b/actions/cherry-picker/index.py
index c8735a5..578cebf 100644
--- a/actions/cherry-picker/index.py
+++ b/actions/cherry-picker/index.py
@@ -40,7 +40,9 @@
 issue_data = requests.get(f"https://api.github.com/repos/{input_data['api_repo_name']}/issues/{pr_number}", headers={'X-GitHub-Api-Version': '2022-11-28'}).json()
 
 # Check if the PR is closed.
-if issue_data["state"] != "closed": raise ValueError(f'The PR #{pr_number} is not closed yet.')
+if issue_data["state"] != "closed":
+    print(f'The PR #{pr_number} is not closed yet.')
+    raise SystemExit(0)
 
 # Retrieve commit_id. If the PR/issue has no commit or has multiple commits, then raise an error.
 commit_id = get_commit_id(pr_number, input_data["actor_name"], input_data["action_event"], input_data["api_repo_name"])