Upgrade to Elasticsearch 7.15.2.

Original Pull Request #1985
Closes #1984

Author: sothawo

Diff for: pom.xml

@@ -18,7 +18,7 @@
 	<url>https://github.com/spring-projects/spring-data-elasticsearch</url>
 
 	<properties>
-		<elasticsearch>7.15.1</elasticsearch>
+		<elasticsearch>7.15.2</elasticsearch>
 		<log4j>2.14.1</log4j>
 		<netty>4.1.65.Final</netty>
 		<springdata.commons>2.6.0-SNAPSHOT</springdata.commons>

Diff for: src/main/asciidoc/preface.adoc

@@ -34,7 +34,7 @@ The following table shows the Elasticsearch versions that are used by Spring Dat
 [cols="^,^,^,^,^",options="header"]
 |===
 | Spring Data Release Train | Spring Data Elasticsearch | Elasticsearch | Spring Framework | Spring Boot
-| 2021.1 (Q)footnote:cdv[Currently in development] | 4.3.xfootnote:cdv[] | 7.15.1 | 5.3.xfootnote:cdv[] | 2.5 .xfootnote:cdv[]
+| 2021.1 (Q)footnote:cdv[Currently in development] | 4.3.xfootnote:cdv[] | 7.15.2 | 5.3.xfootnote:cdv[] | 2.5 .xfootnote:cdv[]
 | 2021.0 (Pascal) | 4.2.x | 7.12.0 | 5.3.x | 2.5.x
 | 2020.0 (Ockham) | 4.1.x | 7.9.3 | 5.3.2 | 2.4.x
 | Neumann | 4.0.x | 7.6.2 | 5.2.12 |2.3.x

Diff for: src/main/asciidoc/reference/elasticsearch-new.adoc

@@ -4,7 +4,7 @@
 [[new-features.4-3-0]]
 == New in Spring Data Elasticsearch 4.3
 
-* Upgrade to Elasticsearch 7.15.1.
+* Upgrade to Elasticsearch 7.15.2.
 * Allow runtime_fields to be defined in the index mapping.
 * Add native support for range field types by using a range object.
 * Add repository search for nullable or empty properties.

Diff for: src/test/resources/testcontainers-elasticsearch.properties

@@ -17,7 +17,7 @@
 # properties defining the image, these are not passed to the container on startup
 #
 sde.testcontainers.image-name=docker.elastic.co/elasticsearch/elasticsearch
-sde.testcontainers.image-version=7.15.1
+sde.testcontainers.image-version=7.15.2
 #
 #
 # needed as we do a DELETE /* at the end of the tests, will be required from 8.0 on, produces a warning since 7.13