docs: reporting-issues.rst: link new document about regressions

docs: reporting-issues.rst: link new document about regressions

Make Documentation/admin-guide/reporting-issues.rst point to the newly
created document about regressions
(Documentation/admin-guide/regressions-regressions.rst). This allows to
shorten a few explanations the new document describes better and in more
detail.

While at it move the copyright hint to the end of the file and remove
quotes around links to other places in the documentation. Both issues
came up during the review of the new documents about regressions.

Signed-off-by: Thorsten Leemhuis <linux@leemhuis.info>
Link: https://lore.kernel.org/r/f20114eaddc356a8c79dd62812a6c7f4ca5d87b9.1644994117.git.linux@leemhuis.info
Signed-off-by: Jonathan Corbet <corbet@lwn.net>