Fix documented default value for workerIsolation property in README.adoc

Author: xsveda

modules/openapi-generator-gradle-plugin/README.adoc

@@ -462,7 +462,7 @@ file states is output.
 
 |workerIsolation
 |String / Provider<String>
-|`process`
+|`classloader`
 a|Controls how the code-generation work action is isolated from the Gradle daemon.
 
 `classloader` (default):: Runs generation inside the Gradle daemon JVM using a separate `ClassLoader`. Avoids the per-task JVM