Remove vestiges of animal sniffer (#31178)

We no longer need animal sniffer because we use JDK functionality
(introduced in JDK 9) to target older versions of the JDK for
compilation. This functionality means that the JDK handles the problem
of ensuring that we do not use JDK APIs from the version that we are
compiling from that are not available in the version that we are
compiling to. A previous commit removed this for the REST client (where
we target JDK 7) but a few traces were left behind.

client/sniffer/src/test/java/org/elasticsearch/client/sniff/ElasticsearchHostsSnifferTests.java

@@ -30,7 +30,6 @@ import com.sun.net.httpserver.HttpServer;
 import org.apache.http.Consts;
 import org.apache.http.HttpHost;
 import org.apache.http.client.methods.HttpGet;
-import org.codehaus.mojo.animal_sniffer.IgnoreJRERequirement;
 import org.elasticsearch.client.Response;
 import org.elasticsearch.client.ResponseException;
 import org.elasticsearch.client.RestClient;
@@ -148,8 +147,6 @@ public class ElasticsearchHostsSnifferTests extends RestClientTestCase {
         return httpServer;
     }
 
-    //animal-sniffer doesn't like our usage of com.sun.net.httpserver.* classes
-    @IgnoreJRERequirement
     private static class ResponseHandler implements HttpHandler {
         private final int sniffTimeoutMillis;
         private final SniffResponse sniffResponse;

client/test/build.gradle

@@ -21,7 +21,6 @@ import org.elasticsearch.gradle.precommit.PrecommitTasks
 import org.gradle.api.JavaVersion
 
 apply plugin: 'elasticsearch.build'
-apply plugin: 'ru.vyarus.animalsniffer'
 
 targetCompatibility = JavaVersion.VERSION_1_7
 sourceCompatibility = JavaVersion.VERSION_1_7
@@ -31,8 +30,6 @@ dependencies {
   compile "com.carrotsearch.randomizedtesting:randomizedtesting-runner:${versions.randomizedrunner}"
   compile "junit:junit:${versions.junit}"
   compile "org.hamcrest:hamcrest-all:${versions.hamcrest}"
-  compile "org.codehaus.mojo:animal-sniffer-annotations:1.15"
-  signature "org.codehaus.mojo.signature:java17:1.0@signature"
 }
 
 forbiddenApisMain {

distribution/tools/launchers/build.gradle

@@ -21,14 +21,11 @@ import org.elasticsearch.gradle.precommit.PrecommitTasks
 import org.gradle.api.JavaVersion
 
 apply plugin: 'elasticsearch.build'
-apply plugin: 'ru.vyarus.animalsniffer'
 
 sourceCompatibility = JavaVersion.VERSION_1_7
 targetCompatibility = JavaVersion.VERSION_1_7
 
 dependencies {
-    signature "org.codehaus.mojo.signature:java17:1.0@signature"
-
     testCompile "com.carrotsearch.randomizedtesting:randomizedtesting-runner:${versions.randomizedrunner}"
     testCompile "junit:junit:${versions.junit}"
     testCompile "org.hamcrest:hamcrest-all:${versions.hamcrest}"