Fix build script to run with Gradle 7 (#191)

Update the Gradle wrapper used to version 7.2 and fixed build.gradle script.

Author: andsel

CHANGELOG.md

@@ -1,3 +1,6 @@
+## Unreleased
+  - Fix: update to Gradle 7 [#191](https://github.com/logstash-plugins/logstash-filter-geoip/pull/191)
+
 ## 7.2.3
   - [DOC] Add documentation for bootstrapping air-gapped environment for database auto-update [#189](https://github.com/logstash-plugins/logstash-filter-geoip/pull/189)
 

gradle/wrapper/gradle-wrapper.properties

@@ -3,4 +3,4 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-6.8-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.2-bin.zip