Use same way to run stuff on main everywhere (IOS-157)

Mastodon/Scene/Onboarding/Login/MastodonLoginViewController.swift

@@ -301,7 +301,7 @@ extension MastodonLoginViewController: MastodonLoginViewModelDelegate {
         
         dataSource?.apply(snapshot, animatingDifferences: false)
         
-        OperationQueue.main.addOperation {
+        DispatchQueue.main.async {
             let numberOfResults = viewModel.filteredServers.count
             self.contentView.updateCorners(numberOfResults: numberOfResults)
         }

Mastodon/Scene/Onboarding/PickServer/PickServerSection.swift

@@ -65,7 +65,7 @@ extension PickServerSection {
         }()
         if let proxiedThumbnail = server.proxiedThumbnail, let thumbnailUrl = URL(string: proxiedThumbnail) {
             cell.thumbnailImageView.af.setImage(withURL: thumbnailUrl, completion: { _ in
-                OperationQueue.main.addOperation {
+                DispatchQueue.main.async {
                     cell.thumbnailImageView.isHidden = false
                 }
             })

Mastodon/Scene/Profile/ProfileViewController.swift

@@ -428,7 +428,7 @@ extension ProfileViewController {
             }
         } receiveValue: { [weak self] menu in
             guard let self = self else { return }
-            OperationQueue.main.addOperation {
+            DispatchQueue.main.async {
               self.moreMenuBarButtonItem.menu = menu
             }
         }

Mastodon/Scene/SuggestionAccount/SuggestionAccountViewController.swift

@@ -124,7 +124,7 @@ extension SuggestionAccountViewController: SuggestionAccountTableViewCellDelegat
 extension SuggestionAccountViewController: SuggestionAccountTableViewFooterDelegate {
     func followAll(_ footerView: SuggestionAccountTableViewFooter) {
         viewModel.followAllSuggestedAccounts(self) {
-            OperationQueue.main.addOperation {
+            DispatchQueue.main.async {
                 self.dismiss(animated: true)
             }
         }