patch 8.2.4311: Vim9: changing script variable type not caught compile time

Problem:    Vim9: changing script variable type not caught at compile time.
Solution:   Set the declared type.
diff --git a/src/vim9instr.c b/src/vim9instr.c
index cf26650..9116f41 100644
--- a/src/vim9instr.c
+++ b/src/vim9instr.c
@@ -1040,7 +1040,7 @@
 
     RETURN_OK_IF_SKIP(cctx);
     if (isn_type == ISN_LOADSCRIPT)
-	isn = generate_instr_type(cctx, isn_type, type);
+	isn = generate_instr_type2(cctx, isn_type, type, type);
     else
 	isn = generate_instr_drop(cctx, isn_type, 1);
     if (isn == NULL)