patch 8.2.1382: Vim9: using :import in filetype plugin gives an error

Problem:    Vim9: using :import in filetype plugin gives an error.
Solution:   Allow commands with the EX_LOCK_OK flag. (closes #6636)
diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index 105710b..96eac7f 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -2087,7 +2087,7 @@
 	// Do allow ":checktime" (it is postponed).
 	// Do allow ":edit" (check for an argument later).
 	// Do allow ":file" with no arguments (check for an argument later).
-	if (!(ea.argt & EX_CMDWIN)
+	if (!(ea.argt & (EX_CMDWIN | EX_LOCK_OK))
 		&& ea.cmdidx != CMD_checktime
 		&& ea.cmdidx != CMD_edit
 		&& ea.cmdidx != CMD_file