Fix compiler warnings regarding loss of data (GH-23983)

diff --git a/Modules/_sqlite/connection.c b/Modules/_sqlite/connection.c
index 5c7b4ee..1e23dac 100644
--- a/Modules/_sqlite/connection.c
+++ b/Modules/_sqlite/connection.c
@@ -1601,7 +1601,7 @@ pysqlite_connection_backup_impl(pysqlite_Connection *self,
 {
     int rc;
     int callback_error = 0;
-    int sleep_ms = sleep * 1000.0;
+    int sleep_ms = (int)(sleep * 1000.0);
     sqlite3 *bck_conn;
     sqlite3_backup *bck_handle;