Privacy: Improve wording on contact upload UI

[manuroe]

We need to follow changes made in Riot Android (element-hq/riot-android@786bf01).

As the Identity Server can be another one than https://vector.im, we must remove "New Vector" from the string.

Current string:
In order to show you which of your contacts are already using Riot or Matrix, we can send the email addresses and phone numbers in your address book to your Matrix Identity Server. New Vector does not store this data or use it for any other purpose. For more information please see the privacy policy page in application settings.

In the dialog context:

[manuroe]

@lampholder , any thoughts about the change we can make for this message?
This message got quite lengthy at 026af21 because Apple required us to be more accurate in order to pass the app review.

This message is static. We cannot format it before the system displays it.

I start with some propositions:

1 - Remove the sentence that mentions NV:
In order to show you which of your contacts are already using Riot or Matrix, we can send the email addresses and phone numbers in your address book to your Matrix Identity Server. For more information please see the privacy policy page in application settings.

but I am not sure that our privacy policy page talks about IS and IS that is not vector.im.

2 - Use a similar string as Android (element-hq/riot-android@786bf01) but in the context of the modal display:
Riot can check your address book to find other Matrix users based on their email and phone numbers.

but I am not sure we will pass Apple review.

[lampholder]

I think we need to share the IS policy docs in the application settings (on Riots mobile and web), though I think we can do this in phase:2. There are some interesting questions about what that looks like - I'll make an issue an boot it in @nadonomy's direction.

Once that's done, we can tell users to check their application settings page for IS policy details. Until then, and to unblock this, how about:
To discover contacts already using Matrix, Riot can send email addresses and phone numbers in your address book to your chosen Matrix identity server. Where supported, personal data is hashed before sending - please check your identity server's privacy policy for more details.