Documentation/process/applying-patches: Activate linux-next man hyperlink

There is a url for linux-next in the 'applying-patches.rst', but it's
surrounded by backquotes.  So the url doesn't have a hyperlink in the
built document.  To let readers easily move to the page, this commit
puts the url outside of the backquotes so that a hyperlink to the url
can be automatically made.
Signed-off-by: SeongJae Park <sjpark@amazon.de>
Link: https://lore.kernel.org/r/20210812095030.4704-1-sj38.park@gmail.comSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/process/applying-patches.rst

@@ -389,7 +389,7 @@ The -mm patches are experimental patches released by Andrew Morton.
 
 In the past, -mm tree were used to also test subsystem patches, but this
 function is now done via the
-`linux-next <https://www.kernel.org/doc/man-pages/linux-next.html>`
+`linux-next` (https://www.kernel.org/doc/man-pages/linux-next.html)
 tree. The Subsystem maintainers push their patches first to linux-next,
 and, during the merge window, sends them directly to Linus.