tools/memory-model: Remove mention of docker/gentoo image

Because the docker and gentoo images haven't been updated in quite some
time, they are likely to provide more confusion than help.  This commit
therefore removes mention of them from the README file.
Reported-by: NAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: akiyks@gmail.com
Cc: boqun.feng@gmail.com
Cc: dhowells@redhat.com
Cc: j.alglave@ucl.ac.uk
Cc: linux-arch@vger.kernel.org
Cc: luc.maranget@inria.fr
Cc: npiggin@gmail.com
Cc: parri.andrea@gmail.com
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/1520443660-16858-2-git-send-email-paulmck@linux.vnet.ibm.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

tools/memory-model/README

@@ -27,21 +27,6 @@ separately:
 
 See "herdtools7/INSTALL.md" for installation instructions.
 
-Alternatively, Abhishek Bhardwaj has kindly provided a Docker image
-of these tools at "abhishek40/memory-model".  Abhishek suggests the
-following commands to install and use this image:
-
-  - Users should install Docker for their distribution.
-  - docker run -itd abhishek40/memory-model
-  - docker attach <id-emitted-from-the-previous-command>
-
-Gentoo users might wish to make use of Patrick McLean's package:
-
-  https://gitweb.gentoo.org/repo/gentoo.git/tree/dev-util/herdtools7
-
-These packages may not be up-to-date with respect to the GitHub
-repository.
-
 
 ==================
 BASIC USAGE: HERD7