ext4: avoid -Wformat-security warning

ext4: avoid -Wformat-security warning

check_igot_inode() prints a variable string, which causes a harmless
warning with 'make W=1':

fs/ext4/inode.c:4763:45: error: format string is not a string literal (potentially insecure) [-Werror,-Wformat-security]
 4763 |         ext4_error_inode(inode, function, line, 0, err_str);

Use a trivial "%s" format string instead.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20250423164354.2780635-1-arnd@kernel.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>