bcachefs: indent error messages of invalid compression

bcachefs: indent error messages of invalid compression

This patch uses printbuf_indent_add_nextline() to set a consistent
indentation level for error messages of invalid compression.

In my previous patch [1], the newline is added by using '\n' in
the argument of prt_str(). This patch replaces prt_str() with
prt_printf() to make indentation level work correctly.

Link: https://lore.kernel.org/20250406152659.205997-2-integral@archlinuxcn.org
Signed-off-by: Integral <integral@archlinuxcn.org>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>