gnome-online-accounts: String freeze break request (GNOME #778416, #778417)

Hey,

I'd like to tweak the following two strings before rolling the 3.23.92
tarball for gnome-online-accounts.

First, https://bugzilla.gnome.org/show_bug.cgi?id=778416:
- "Microsoft Account"
+ "Microsoft"

Otherwise in various places where we use "<provider-name> Account", it
becomes "Microsoft Account Account".

Second, https://bugzilla.gnome.org/show_bug.cgi?id=778417:
- "% account"
+ "% Account"

This is to make the capitalization of the dialog titles
consistent. The new string already exists in
gnome-control-center/panels/online-accounts, but sadly due to various
details I couldn't get rid of the copy in gnome-online-accounts. I
hope to solve that in the near future.

What do you think?

Cheers,
Rishi