LU-15233 llite: Remove extra cl_page_delete call

LU-15233 llite: Remove extra cl_page_delete call

"LU-5108 osc: Performance tune for LRU" added a call to
cl_page_delete to the page discard code used by the OSC
lru shrinker.

This seems to have been a mistake.  cl_page_discard causes
page invalidation, which calls ll_invalidatepage, which
calls cl_page_delete if the page can be found.

Since the page is locked here and ll_invalidatepage checks
for the cl_page, this extra call to cl_pege_delete has
probably never caused an issue.

But it's extraneous and kind of weird, and misled me a bit
when working on another bug.  Let's remove it.

Fixes: b117bc837c02 ("LU-5108 osc: Performance tune for LRU")
Signed-off-by: Patrick Farrell <pfarrell@whamcloud.com>
Change-Id: I1380f532359ba949a0bbb8b53227a6c8e6491030
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/45583
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Qian Yingjin <qian@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>