iOS: remove desktop sources that were mistakenly merged into app/CMakeLists.txt (#868)

Co-authored-by: Ari Zigler <[email protected]>

Author: arizigler

app/CMakeLists.txt

@@ -158,8 +158,6 @@ set(app_android_SRCS
 set(app_ios_SRCS
     src/app_ios.mm
     src/util_ios.mm
-    src/heartbeat_date_storage_desktop.cc
-    src/heartbeat_info_desktop.cc
     src/invites/ios/invites_receiver_internal_ios.mm
     src/invites/ios/invites_ios_startup.mm
     src/uuid_ios_darwin.mm)