patch 8.2.2225: Vim9: error when using :import in legacy script twice

Problem:    Vim9: error when using :import in legacy script twice.
Solution:   Make it possible to redefine an import when reloading.
diff --git a/src/proto/vim9script.pro b/src/proto/vim9script.pro
index 3603b0b..c386602 100644
--- a/src/proto/vim9script.pro
+++ b/src/proto/vim9script.pro
@@ -4,6 +4,7 @@
 int not_in_vim9(exarg_T *eap);
 void ex_export(exarg_T *eap);
 void free_imports_and_script_vars(int sid);
+void mark_imports_for_reload(int sid);
 void ex_import(exarg_T *eap);
 int find_exported(int sid, char_u *name, ufunc_T **ufunc, type_T **type, cctx_T *cctx);
 char_u *handle_import(char_u *arg_start, garray_T *gap, int import_sid, evalarg_T *evalarg, void *cctx);