update the google play icons

[DenBond7]

We have to update the google play icons to fit the requirements(https://developer.android.com/google-play/resources/icon-design-specifications). It's not urgent. I'll create an issue for that and attach icons.

[tomholub]

@limonte will look at it later at https://github.com/FlowCrypt/flowcrypt-design/issues/20