override byte TCK tests

com.oracle.truffle.r.test/src/com/oracle/truffle/r/test/tck/FastRTckTest.java

@@ -274,6 +274,16 @@ public class FastRTckTest extends TruffleTCK {
         // no longs in FastR
     }
 
+    @Override
+    public void testPlusWithBytes() throws Exception {
+        // no bytes in FastR
+    }
+
+    @Override
+    public void testPlusWithOneNegativeByte() throws Exception {
+        // no bytes in FastR
+    }
+
     @Override
     public void testPlusWithShort() throws Exception {
         // no shorts in FastR