Remove unused imports

Author: eregon

src/main/java/org/truffleruby/core/kernel/KernelNodes.java

@@ -145,7 +145,6 @@
 import java.nio.file.Paths;
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Collection;
 import java.util.List;
 import java.util.concurrent.TimeUnit;
 

src/main/java/org/truffleruby/language/globals/AliasGlobalVarNode.java

@@ -9,10 +9,8 @@
  */
 package org.truffleruby.language.globals;
 
-import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
 import com.oracle.truffle.api.frame.VirtualFrame;
 import org.truffleruby.language.RubyNode;
-import org.truffleruby.language.control.RaiseException;
 
 public class AliasGlobalVarNode extends RubyNode {
 

src/main/java/org/truffleruby/language/globals/WriteSimpleGlobalVariableNode.java

@@ -1,7 +1,5 @@
 package org.truffleruby.language.globals;
 
-import com.oracle.truffle.api.object.DynamicObject;
-import org.truffleruby.Layouts;
 import org.truffleruby.core.basicobject.BasicObjectNodes.ReferenceEqualNode;
 import org.truffleruby.language.RubyBaseNode;
 import org.truffleruby.language.objects.shared.WriteBarrierNode;