fix: searching background UI issue

Mastodon/Scene/Search/SearchViewController+Searching.swift

@@ -29,6 +29,7 @@ extension SearchViewController {
             searchingTableView.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor),
         ])
         searchingTableView.tableFooterView = UIView()
+        searchingTableView.backgroundColor = Asset.Colors.Background.systemGroupedBackground.color
         viewModel.isSearching
             .receive(on: DispatchQueue.main)
             .sink { [weak self] isSearching in

Mastodon/Scene/Search/TableViewCell/SearchingTableViewCell.swift

@@ -54,7 +54,7 @@ final class SearchingTableViewCell: UITableViewCell {
 
 extension SearchingTableViewCell {
     private func configure() {
-        backgroundColor = .clear
+        backgroundColor = Asset.Colors.Background.systemBackground.color
         
         let containerStackView = UIStackView()
         containerStackView.axis = .horizontal