Update mongo

Changes:

- https://github.com/docker-library/mongo/commit/687a397: Update to 3.4.23
- https://github.com/docker-library/mongo/commit/4b492e2: Update generated README

library/mongo

@@ -4,17 +4,17 @@ Maintainers: Tianon Gravi <[email protected]> (@tianon),
              Joseph Ferguson <[email protected]> (@yosifkit)
 GitRepo: https://github.com/docker-library/mongo.git
 
-Tags: 3.4.22-xenial, 3.4-xenial
-SharedTags: 3.4.22, 3.4
+Tags: 3.4.23-xenial, 3.4-xenial
+SharedTags: 3.4.23, 3.4
 # see http://repo.mongodb.org/apt/ubuntu/dists/xenial/mongodb-org/3.4/multiverse/
 Architectures: amd64, arm64v8
-GitCommit: ebd79727e4e77210272ec55c8b22b17877bfd29a
+GitCommit: 687a397947f374e3bd6dbdf00a98753584833d96
 Directory: 3.4
 
-Tags: 3.4.22-windowsservercore-ltsc2016, 3.4-windowsservercore-ltsc2016
-SharedTags: 3.4.22-windowsservercore, 3.4-windowsservercore, 3.4.22, 3.4
+Tags: 3.4.23-windowsservercore-ltsc2016, 3.4-windowsservercore-ltsc2016
+SharedTags: 3.4.23-windowsservercore, 3.4-windowsservercore, 3.4.23, 3.4
 Architectures: windows-amd64
-GitCommit: ebd79727e4e77210272ec55c8b22b17877bfd29a
+GitCommit: 687a397947f374e3bd6dbdf00a98753584833d96
 Directory: 3.4/windows/windowsservercore-ltsc2016
 Constraints: windowsservercore-ltsc2016