Fix warning in idea gradle sync (elastic#138749) (elastic#138861)

This simplifies the expand map in client:rest to use a simple model that
is understood by Idea

This api also has a known flaw of memory issues and we use ReplaceTokens already in other places

Author: breskeby

client/rest/build.gradle

@@ -20,6 +20,7 @@ import org.elasticsearch.gradle.internal.precommit.CheckForbiddenApisTask
 
 import org.elasticsearch.gradle.VersionProperties
 import org.elasticsearch.gradle.internal.conventions.precommit.LicenseHeadersTask
+import org.apache.tools.ant.filters.ReplaceTokens
 
 apply plugin: 'elasticsearch.build'
 apply plugin: 'elasticsearch.publish'
@@ -55,9 +56,9 @@ dependencies {
 }
 
 tasks.named("processResources").configure {
-  expand versions: [
-    elasticsearch: VersionProperties.getElasticsearch()
-  ]
+  def expansions = [elasticsearch:VersionProperties.getElasticsearch()]
+  inputs.properties(expansions)
+  filter(ReplaceTokens, tokens:expansions)
 }
 
 tasks.withType(CheckForbiddenApisTask).configureEach {

client/rest/src/main/resources/org/elasticsearch/client/version.properties

@@ -15,4 +15,4 @@
 # specific language governing permissions and limitations
 # under the License.
 
-elasticsearch-client=${versions.elasticsearch}
+elasticsearch-client=@elasticsearch@