README: Fix spelling/capitalization

- Fix spelling/capitalization s/Restructured/ReStructured/
Signed-off-by: Thorsten Blum <thorsten.blum@toblux.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20240207122127.9182-1-thorsten.blum@toblux.com

README

@@ -11,7 +11,7 @@ In order to build the documentation, use ``make htmldocs`` or
     https://www.kernel.org/doc/html/latest/
 
 There are various text files in the Documentation/ subdirectory,
-several of them using the Restructured Text markup notation.
+several of them using the ReStructured Text markup notation.
 
 Please read the Documentation/process/changes.rst file, as it contains the
 requirements for building and running the kernel, and information about