Email notifications don't work if git branch name > 22 characters

**Describe the bug**
Email notifications don't work if the name of the git branch exceeds 22 characters

**To Reproduce**
Steps to reproduce the behavior:

1. Set up a React app or similar in a git branch with a name longer than 22 chars (e.g. `abcdefghijklmnopqrstuv` - 23 chars) - note: only tested with Bitbucket
2. Go to AWS Amplify console, click "Connect app" and follow instructions to connect above app
3. Go to the "Email notifications" setting in the left hand menu and click "Add notification"
4. Add your email address, select the above git branch, and hit "Save"
5. The message `Notification creation : in progress...` appears at the top of the screen with a spinner - this message never goes away
6. You should receive an email asking you to confirm that you wish to subscribe to the SNS Topic
7. You do not receive any emails about builds of your Amplify app

**Expected behavior**
After entering an email address, selecting a git branch, and hitting "Save" when adding an email notification, the message `Notification creation : in progress...` should eventually change to the message `Success...`. It should send emails to you when a build starts/fails/succeeds.

**Code Snippet**
Not really a code snippet, but if the git branch has the name `abcdefghijklmnopqrstuv` (23 chars) then the problem occurs and if the git branch has the name `abcdefghijklmnopqrstu` (22 chars) then it does not.

**Screenshots**
N/A

Start by reproducing the issue in the AWS Amplify console using the described Bitbucket branch-length boundary: 22 characters should work and 23 should fail. Trace the Email notifications "Add notification" flow and its build notification handling. Done means creation reaches "Success..." and build-start, failure, and success emails are delivered for branches longer than 22 characters.

Written by the indexing model from the issue text.