Upgrade icu4j for the ICU analysis plugin to 59.1 (#25243)

* Upgrade icu4j for the ICU analysis plugin to 59.1

Lucene upgraded to 59.1 so we should use the same.

Closes #21425

* Add breaking change for the icu upgrade

docs/reference/migration/migrate_6_0/plugins.asciidoc

@@ -73,3 +73,10 @@ and `cloud.aws.ec2.region`. Instead, specify the full endpoint.
 
 Previous versions of Elasticsearch would skip hidden files and directories when
 scanning the plugins folder. This leniency has been removed.
+
+==== ICU Analysis plugin
+
+The icu4j library has been upgraded to 59.1,
+Indices created in the previous major version will need to be reindexed
+in order to return correct (and correctly ordered) results,
+and to take advantage of new characters.

plugins/analysis-icu/build.gradle

@@ -24,7 +24,7 @@ esplugin {
 
 dependencies {
   compile "org.apache.lucene:lucene-analyzers-icu:${versions.lucene}"
-  compile 'com.ibm.icu:icu4j:56.1'
+  compile 'com.ibm.icu:icu4j:59.1'
 }
 
 dependencyLicenses {

plugins/analysis-icu/licenses/icu4j-56.1.jar.sha1

@@ -1 +0,0 @@
-8dd6671f52165a0419e6de5e1016400875a90fa9

plugins/analysis-icu/licenses/icu4j-59.1.jar.sha1

@@ -0,0 +1 @@
+6f06e820cf4c8968bbbaae66ae0b33f6a256b57f