[Android] Users with unsupported Android versions (<6) can wrongly install the app from Google Play store

[SoftVision-CiprianMuresan]

[Notes]:

• We're getting quite a few reports from users using unsupported Android versions (under 6). Where we have serious issues (app crashes at login, missing placeholders when animations are turned off).
• See App crashes when trying to login #1344, No hint about progress during sign in when system animation is turned off #1342.
• We should be able to specify what Android versions are supported so that users with unsupported Android versions can't install the app from Google Play Store.

[Affected Platforms]:

• Android versions under 6

[Steps to reproduce]:

1. Open the Google Play Store app.
2. Navigate to the Notes by Firefox app page.
3. Observe the page.

[Expected results]:

• "This device is not supported" message is displayed.

[Actual results]:

• The Install button is displayed.

[Softvision-MariusComan]

This issue is still reproducible, the Android 5 users will still be able to install the app from "Google Play" store, even if this Android version is still unsupported. Considering this I am reopening this issue.