api: remove unused dc_accounts_all_work_done() (#5384)

it was used by iOS to know when a background fetch was complete;
meanwhile the superiour `dc_accounts_background_fetch()` is used for
that.

there is still the corresponding context function `dc_all_work_done()`,
this not used by any UI as well, however, it is in use by a python
tests.

not sure, what to do with it, at a first glance, the test still seems
useful.

src/accounts.rs

@@ -253,25 +253,6 @@ impl Accounts {
         self.accounts.keys().copied().collect()
     }
 
-    /// This is meant especially for iOS, because iOS needs to tell the system when its background work is done.
-    ///
-    /// Returns whether all accounts finished their background work.
-    /// DC_EVENT_CONNECTIVITY_CHANGED will be sent when this turns to true.
-    ///
-    /// iOS can:
-    /// - call dc_start_io() (in case IO was not running)
-    /// - call dc_maybe_network()
-    /// - while dc_accounts_all_work_done() returns false:
-    ///   -  Wait for DC_EVENT_CONNECTIVITY_CHANGED
-    pub async fn all_work_done(&self) -> bool {
-        for account in self.accounts.values() {
-            if !account.all_work_done().await {
-                return false;
-            }
-        }
-        true
-    }
-
     /// Starts background tasks such as IMAP and SMTP loops for all accounts.
     pub async fn start_io(&mut self) {
         for account in self.accounts.values_mut() {

src/scheduler/connectivity.rs

@@ -170,7 +170,7 @@ impl ConnectivityStore {
 }
 
 /// Set all folder states to InterruptingIdle in case they were `Connected` before.
-/// Called during `dc_maybe_network()` to make sure that `dc_accounts_all_work_done()`
+/// Called during `dc_maybe_network()` to make sure that `dc_all_work_done()`
 /// returns false immediately after `dc_maybe_network()`.
 pub(crate) async fn idle_interrupted(inbox: ConnectivityStore, oboxes: Vec<ConnectivityStore>) {
     let mut connectivity_lock = inbox.0.lock().await;