Update primitive name.

Author: aardvark179

src/main/java/org/truffleruby/core/encoding/EncodingNodes.java

@@ -676,7 +676,7 @@ private DynamicObject replicate(String name, Encoding encoding) {
 
     }
 
-    @Primitive(name = "dummy_encoding", needsSelf = false)
+    @Primitive(name = "encoding_create_dummy", needsSelf = false)
     public static abstract class DummyEncodingeNode extends PrimitiveArrayArgumentsNode {
 
         @Specialization(guards = "isRubyString(nameObject)")

src/main/ruby/core/truffle/encoding_operations.rb

@@ -11,7 +11,7 @@
 module Truffle
   module EncodingOperations
     def self.dummy_encoding(name)
-      new_encoding, index = Truffle.invoke_primitive :dummy_encoding, name
+      new_encoding, index = Truffle.invoke_primitive :encoding_create_dummy, name
       ::Encoding::EncodingMap[name.upcase.to_sym] = [nil, index]
       [new_encoding, index]
     end