README.rst: Trim outdated .EXCLUSIVE snippets

It looks like these sections got duplicated somehow. I've kept only the portalocker.LOCK_EX snippet, since it seems to be the only valid flag presently.

README.rst

@@ -121,38 +121,6 @@ To make sure your cache generation scripts don't race, use the `Lock` class:
 
 To customize the opening and locking a manual approach is also possible:
 
->>> import portalocker
->>> file = open('somefile', 'r+')
->>> portalocker.lock(file, portalocker.EXCLUSIVE)
->>> file.seek(12)
->>> file.write('foo')
->>> file.close()
-
-Explicitly unlocking is not needed in most cases but omitting it has been known
-to cause issues:
-
->>> import portalocker
->>> with portalocker.Lock('somefile', timeout=1) as fh:
-...     print >>fh, 'writing some stuff to my cache...'
-
-To customize the opening and locking a manual approach is also possible:
-
->>> import portalocker
->>> file = open('somefile', 'r+')
->>> portalocker.lock(file, portalocker.EXCLUSIVE)
->>> file.seek(12)
->>> file.write('foo')
->>> file.close()
-
-Explicitly unlocking is not needed in most cases but omitting it has been known
-to cause issues:
-
->>> import portalocker
->>> with portalocker.Lock('somefile', timeout=1) as fh:
-...     print >>fh, 'writing some stuff to my cache...'
-
-To customize the opening and locking a manual approach is also possible:
-
 >>> import portalocker
 >>> file = open('somefile', 'r+')
 >>> portalocker.lock(file, portalocker.LOCK_EX)