Remove LegacySessionImporter

[bmarty]

Type of change

• Feature
• Bugfix
• Technical
• Other :

Content

Remove LegacySessionImporter, and the dialog which explains that Riot is now Element.

Motivation and context

We can consider that users and even fork are all migrated to Element now. Also keeping the LegacySessionImporter will require more work to migrate to ElementR and to ElementX.

Drawback: If by any chance user upgrades from Riot to Element after the PR is merged, the user will have to login again, and the legacy data will not be deleted from the device.

Screenshots / GIFs

Tests

• Start the app.

Tested devices

• Physical
• Emulator
• OS version(s):

Checklist

• Changes has been tested on an Android device or Android emulator with API 21
• UI change has been tested on both light and dark themes
• Accessibility has been taken into account. See https://github.com/vector-im/element-android/blob/develop/CONTRIBUTING.md#accessibility
• Pull request is based on the develop branch
• Pull request includes a new file under ./changelog.d. See https://github.com/vector-im/element-android/blob/develop/CONTRIBUTING.md#changelog
• Pull request includes screenshots or videos if containing UI changes
• Pull request includes a sign off
• You've made a self review of your PR
• If you have modified the screen flow, or added new screens to the application, you have updated the test UiAllScreensSanityTest.allScreensTest()

[BillCarsonFr]

LGTM

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
4 Code Smells

No Coverage information
0.0% Duplication