Merge pull request #165 from hmcts/renovate/checkstyle-10.x

Update dependency checkstyle to v10.18.1

build.gradle

@@ -96,7 +96,7 @@ publishing {
 
 checkstyle {
     maxWarnings = 0
-    toolVersion = '10.17.0'
+    toolVersion = '10.18.1'
     // need to set configDir to rootDir otherwise submodule will use submodule/config/checkstyle
     configDirectory = new File(rootDir, 'config/checkstyle')
 }