docs/ja_JP/howto: Update for v6.1

docs/ja_JP/howto: Update for v6.1

Reflect changes made in commits listed below:

  388f9b20f98d ("Documentation/process/howto: Only send regression fixes after -rc1").
  bc0ef4a7e4c3 ("Doc: Delete reference to the kernel-mentors mailing list")
  bcd3cf0855c5 ("Doc: Remove outdated info about bugzilla mailing lists")
  dad051395413 ("Doc: add a missing cross-reference")
  9799445af124 ("Doc: tidy up TOCs and refs to license-rules.rst")
  fb0e0ffe7fc8 ("Documentation: bring process docs up to date")
  e7b4311ebcac ("Replace HTTP links with HTTPS ones: Documentation/process")
  f1eebe92c265 ("Documentation/HOWTO: adjust external link references")
  da514157c4f0 ("docs: make reporting-bugs.rst obsolete")
  cf6d6fc27936 ("docs: process/howto.rst: make sections on bug reporting match practice")

Co-developed-by: Kosuke Fujimoto <fujimotokosuke0@gmail.com>
Signed-off-by: Kosuke Fujimoto <fujimotokosuke0@gmail.com>
Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Cc: Tsugikazu Shibata <shibata@linuxfoundation.org>
Acked-by: Tsugikazu Shibata <shibata@linuxfoundation.org>
Link: https://lore.kernel.org/r/20221030115209.25924-1-akiyks@gmail.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>