Documentation: riscv: fix insufficient list item indent

When adding the ISA string ordering rules, I didn't sufficiently indent
one of the list items.

Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/linux-doc/202301300743.bp7Dpazv-lkp@intel.com/


Fixes: f07b2b3f ("Documentation: riscv: add a section about ISA string ordering in /proc/cpuinfo")
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
Link: https://lore.kernel.org/r/20230129235701.2393241-1-conor@kernel.org


Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>