fix: Redirects old Explore URLs to the new one (apache#20812)

(cherry picked from commit 34278c2)

superset/views/core.py

@@ -752,6 +752,9 @@ def explore(
             "This API endpoint is deprecated and will be removed in version 3.0.0",
             self.__class__.__name__,
         )
+        if request.method == "GET":
+            return redirect(request.url.replace("/superset/explore", "/explore"))
+
         initial_form_data = {}
 
         form_data_key = request.args.get("form_data_key")