change mcp server collection to use webpki roots instead of native, since the native roots do not work on android

mcp_server_collection/src/caldav/client.rs

@@ -24,8 +24,7 @@ pub(crate) fn get_caldav_client(
     password: &str,
 ) -> AuthorizedCaldavClient {
     let https_connector: HttpsConnector<HttpConnector> = HttpsConnectorBuilder::new()
-        .with_native_roots()
-        .unwrap()
+        .with_webpki_roots()
         .https_only()
         .enable_http1()
         .build();