kbuild: edit explanation of clean-files variable

Commit 976591810f (kbuild Update documentation of clean-files and clean-dirs)
changed the example for the clean-files variable, but left the explanation
unchanged. Edit the explanation to match the example.

Signed-off-by: Jeffrey Rogers <jeffreydavidrogers@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/kbuild/makefiles.txt

@@ -755,8 +755,8 @@ Additional files can be specified in kbuild makefiles by use of $(clean-files).
 		#lib/Makefile
 		clean-files := crc32table.h
 
-When executing "make clean", the two files "devlist.h classlist.h" will be
-deleted. Kbuild will assume files to be in the same relative directory as the
+When executing "make clean", the file "crc32table.h" will be deleted.
+Kbuild will assume files to be in the same relative directory as the
 Makefile, except if prefixed with $(objtree).
 
 To delete a directory hierarchy use: