patch 8.2.2182: Vim9: value of 'magic' is still relevant

Problem:    Vim9: value of 'magic' is still relevant.
Solution:   Always behave like 'magic' is on in Vim9 script (closes #7509)
diff --git a/src/arglist.c b/src/arglist.c
index dd255a6..4e971fd 100644
--- a/src/arglist.c
+++ b/src/arglist.c
@@ -409,7 +409,7 @@
 	    p = file_pat_to_reg_pat(p, NULL, NULL, FALSE);
 	    if (p == NULL)
 		break;
-	    regmatch.regprog = vim_regcomp(p, p_magic ? RE_MAGIC : 0);
+	    regmatch.regprog = vim_regcomp(p, magic_isset() ? RE_MAGIC : 0);
 	    if (regmatch.regprog == NULL)
 	    {
 		vim_free(p);