fix(ios,build) use epoch seconds for build number

Avoids conflicts when a build is rejected by Apple since Fastlane cannot
detect it.

ios/fastlane/Fastfile

@@ -71,7 +71,7 @@ platform :ios do
 
     # Inrement the build number by 1
     increment_build_number(
-      build_number: latest_testflight_build_number + 1,
+      build_number: Time.now.to_i,
       xcodeproj: "app/app.xcodeproj"
     )