我刚找到一种方法把它取出来。删除搜索栏上方空间的方法是避免使用内置的.searchable修饰符，而是通过创建UIViewRepresentable SwiftUI视图来使用UIKit的UISearchBar。这使您可以完全控制搜索栏的外观和行为。下面是一个如何执行此操作的示例：
首先，创建SearchBar结构：

import SwiftUI

struct SearchBar: UIViewRepresentable {
    
    @Binding var text: String
    var placeholder: String
    
    func makeUIView(context: UIViewRepresentableContext<SearchBar>) -> UISearchBar {
        let searchBar = UISearchBar(frame: .zero)
        searchBar.delegate = context.coordinator
        searchBar.searchBarStyle = .minimal
        searchBar.placeholder = placeholder
        searchBar.autocapitalizationType = .none
        return searchBar
    }
    
    func updateUIView(_ uiView: UISearchBar, context: UIViewRepresentableContext<SearchBar>) {
        uiView.text = text
    }
    
    func makeCoordinator() -> SearchBar.Coordinator {
        return Coordinator(text: $text)
    }
    
    class Coordinator: NSObject, UISearchBarDelegate {
        @Binding var text: String
        
        init(text: Binding<String>) {
            _text = text
        }
        
        func searchBar(_ searchBar: UISearchBar, textDidChange searchText: String) {
            text = searchText
        }
    }
}

然后，您可以在SwiftUI视图中使用SearchBar，如下所示：

struct ContentView: View {
    @State private var searchText = ""

    var body: some View {
        VStack {
            SearchBar(text: $searchText, placeholder: "Search")
            // Your other views here...
        }
    }
}

这将在SwiftUI视图的顶部给予一个搜索栏。