backup: disable feature

Disable this feature for the release since it does not work with a
Ring multidevice account.
We simply hide the button allowing to use the Restore/Back up an account

Change-Id: Ib13cd3d27497ccef1b0c4516a3659f32fb8b7bb2
Tuleap: #1161
diff --git a/ui/Base.lproj/Accounts.xib b/ui/Base.lproj/Accounts.xib
index 7707007..b8efed3 100644
--- a/ui/Base.lproj/Accounts.xib
+++ b/ui/Base.lproj/Accounts.xib
@@ -188,7 +188,7 @@
                         <action selector="removeAccount:" target="-2" id="nTB-Tc-25y"/>
                     </connections>
                 </button>
-                <button verticalHuggingPriority="750" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="nRs-ZL-bau">
+                <button hidden="YES" verticalHuggingPriority="750" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="nRs-ZL-bau">
                     <rect key="frame" x="95" y="30" width="25" height="19"/>
                     <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
                     <buttonCell key="cell" type="smallSquare" bezelStyle="smallSquare" image="NSActionTemplate" imagePosition="overlaps" alignment="center" lineBreakMode="truncatingTail" state="on" imageScaling="proportionallyDown" inset="2" id="q7p-0B-d1J">