LU-10215 tests: remove disk2_4 disk2_5 images

LU-10215 tests: remove disk2_4 disk2_5 images

Remove the old disk2_4-*.tar.bz2 and disk2_5-ldiskfs.tar.bz2
images from the Git repo.  The disk2_5 image was never included into
testing due to an oversight in Makefile.am, and adding it to testing
is unlikely to be of any practical value as these releases are both
more than 10 years old and very unlikely to have any users that would
actually want to upgrade their systems at this point.

Lustre-change: https://review.whamcloud.com/47281
Lustre-commit: add70ce9cdc3e2d6148dafeef587d12d0277744c

Test-Parameters: trivial
Test-Parameters: testlist=conf-sanity env=ONLY=32 mdscount=1 mdtcount=1
Test-Parameters: testlist=conf-sanity env=ONLY=32 mdscount=2 mdtcount=4
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: I76a42eb90c3e1198d33783f3089ac30462429ac4
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Signed-off-by: Li Dongyang <dongyangli@ddn.com>
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/55444
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>