fix(coverity/532324): free skip_until to prevent leak #36109

src/nvim/eval/userfunc.c

@@ -2574,6 +2574,7 @@ static int get_function_body(exarg_T *eap, garray_T *newlines, char *line_arg_in
               heredoc_trimmedlen = (size_t)(skipwhite(theline) - theline);
               heredoc_trimmed = xmemdupz(theline, heredoc_trimmedlen);
             }
+            XFREE_CLEAR(skip_until);
             skip_until = xmemdupz(p, (size_t)(skiptowhite(p) - p));
             do_concat = false;
             is_heredoc = true;