Set release date

LTS-CHANGELOG.adoc

@@ -18,7 +18,7 @@ The LTS changelog lists releases which are only accessible via a commercial subs
 All fixes and changes in LTS releases will be released the next minor release. Changes from LTS 1.4.x will be included in release 1.5.0.
 
 [[v1.8.18]]
-== 1.8.18 (TBD)
+== 1.8.18 (22.02.2023)
 
 icon:check[] Search: The search endpoints (like e.g. `/api/v1/search/nodes`) were incorrectly treated as not "read-only", which caused them to fail during a cluster topology change,
 if the setting `cluster.topologyChangeReadOnly` was set to `true`. This has been changed now, the real search endpoints are read-only now. It is important to note, that this does still