[Auth] Remove the .showLoginEmail segue and navigate programmatically

[mindgraffiti]

Ref. #2003.

In this PR

• TIL that Cocoapods does not like our beta versions and will ignore newer beta versions, so I made the beta versions explicit in the podfile.
• Authenticator has been updated to remove the storyboard segue .showLoginEmail
• See also Remove segue .showLoginEmail wordpress-mobile/WordPressAuthenticator-iOS#207

To Test

1. Check out this branch
2. rake dependencies
3. Run unit tests
4. Build and run
5. Log out
6. Select the "Log in with Jetpack" button.

Do not merge until

1. The Authenticator PR has been merged: Remove segue .showLoginEmail wordpress-mobile/WordPressAuthenticator-iOS#207 ✔️
2. A new Authenticator release has been created ✔️
3. The release is published on Cocoapods trunk ✔️
4. This PR points to the new release ✔️

Expected result: it should show the expected LoginEmailViewController

Update release notes:

• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[shiki]

@mindgraffiti It looks like there are conflicts in Podfile and Podfile.lock. 🙂

[peril-woocommerce]

You can trigger an installable build for these changes by visiting CircleCI here.

[mindgraffiti]

@shiki fixed 🙂

[shiki]

Thanks, @mindgraffiti! I have a question about the pod versions.

• Tested login with site address
• Tested login with Jetpack
• Quickly glanced at wordpress-mobile/WordPressAuthenticator-iOS#207 to see what's changed

[shiki]

Looks good, Thuy! Thank you for reverting the Podfile change. And sorry for the delay!

[mindgraffiti]

Thank you @shiki !