[jdk11u-dev] RFR: 8292887: Bump update version for OpenJDK: jdk-11.0.18

[Christoph Langer]

Prepare for 11.0.18 development.

-------------

Commit messages:
 - JDK-8292887

Changes: https://git.openjdk.org/jdk11u-dev/pull/1342/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=1342&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8292887
  Stats: 3 lines in 2 files changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/1342.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev pull/1342/head:pull/1342

PR: https://git.openjdk.org/jdk11u-dev/pull/1342