Help: Update file(ARCHIVE...) synopsis for renamed options

The FILES and DIRECTORY options were renamed in bbcff21f71
(file(ARCHIVE*): Collapse FILES and DIRECTORY options, 2020-06-30), 
but the synopsis part of the file() documentation was missed.
The synopsis also typically only shows the mandatory options.
Update the synopsis to reflect the name changes and omit the
DESTINATION option since it is not mandatory.

Help/command/file.rst

@@ -43,8 +43,8 @@ Synopsis
     file(`LOCK`_ <path> [...])
 
   `Archiving`_
-    file(`ARCHIVE_CREATE`_ OUTPUT <archive> FILES <files> [...])
-    file(`ARCHIVE_EXTRACT`_ INPUT <archive> DESTINATION <dir> [...])
+    file(`ARCHIVE_CREATE`_ OUTPUT <archive> PATHS <paths>... [...])
+    file(`ARCHIVE_EXTRACT`_ INPUT <archive> [...])
 
 Reading
 ^^^^^^^