Remove Encoding workaround

src/System.Private.CoreLib/src/System/Text/Encoding.cs

@@ -288,13 +288,7 @@ public static Encoding GetEncoding(int codepage)
             if (s_encodings == null)
                 Interlocked.CompareExchange<EncodingCache>(ref s_encodings, new EncodingCache(), null);
 
-#if CORERT
-            // CORERT-TODO: For now, always return UTF8 encoding
-            // https://github.com/dotnet/corert/issues/213
-            return UTF8;
-#else
             return s_encodings.GetOrAdd(codepage);
-#endif
         }
 
         private sealed class EncodingCache : ConcurrentUnifier<int, Encoding>
@@ -418,13 +412,7 @@ public static Encoding GetEncoding(String name)
             // Otherwise, the code below will throw exception when trying to call
             // EncodingTable.GetCodePageFromName().
             //
-#if CORERT
-            // CORERT-TODO: For now, always return UTF8 encoding
-            // https://github.com/dotnet/corert/issues/213
-            return UTF8;
-#else
             return GetEncoding(EncodingTable.GetCodePageFromName(name));
-#endif
         }
 
         // Returns an Encoding object for a given name or a given code page value.