Update Airbitz to [validation: "checkpassvalidationservers"] since it connects to multiple, public Electrum servers for non-SPV validation

Also update iOS and Android screenshots

_templates/choose-your-wallet.html

@@ -228,7 +228,7 @@ wallets:
         - ios
         check:
           control: "checkpasscontrolhybrid"
-          validation: "checkfailvalidationcentralized"
+          validation: "checkpassvalidationservers"
           transparency: "checkpasstransparencyopensource"
           environment: "checkpassenvironmentmobile"
           privacy: "checkpassprivacybasic"
@@ -245,7 +245,7 @@ wallets:
         - android
         check:
           control: "checkpasscontrolhybrid"
-          validation: "checkfailvalidationcentralized"
+          validation: "checkpassvalidationservers"
           transparency: "checkpasstransparencyopensource"
           environment: "checkpassenvironmentmobile"
           privacy: "checkpassprivacybasic"
@@ -262,7 +262,7 @@ wallets:
         - ios
         check:
           control: "checkpasscontrolhybrid"
-          validation: "checkfailvalidationcentralized"
+          validation: "checkpassvalidationservers"
           transparency: "checkpasstransparencyopensource"
           environment: "checkpassenvironmentmobile"
           privacy: "checkpassprivacybasic"