Settings - Security: Move down the key backup section

With cross-signing and SSSS, this section is less important.

Riot/Modules/Settings/Security/SecurityViewController.m

@@ -33,9 +33,9 @@
 enum
 {
     SECTION_CRYPTO_SESSIONS,
-    SECTION_KEYBACKUP,
     SECTION_CROSSSIGNING,
     SECTION_CRYPTOGRAPHY,
+    SECTION_KEYBACKUP,
     SECTION_ADVANCED,
     SECTION_COUNT
 };