Fixed "Task with name 'deobfuscateJar' not found in root project" in multi-project build

```
A problem occurred configuring project ':mod'.
> Task with name 'deobfuscateJar' not found in root project 'testProject'.
```

Stacktrace:
```
org.gradle.api.ProjectConfigurationException: A problem occurred configuring project ':mod'.
        at org.gradle.configuration.project.LifecycleProjectEvaluator.addConfigurationFailure(LifecycleProjectEvaluator.java:79)
...
Caused by: org.gradle.api.UnknownTaskException: Task with name 'deobfuscateJar' not found in root project 'testProject'.
        at org.gradle.api.internal.tasks.DefaultTaskCollection.createNotFoundException(DefaultTaskCollection.java:85)
        at org.gradle.api.internal.DefaultNamedDomainObjectCollection.getByName(DefaultNamedDomainObjectCollection.java:192)
        at org.gradle.api.internal.tasks.DefaultTaskCollection.getByName(DefaultTaskCollection.java:34)
        at net.minecraftforge.gradle.user.UserBasePlugin$1$1.execute(UserBasePlugin.java:113)
```