removed the modifyMaterials method from AES + RSA Keyrings since it will already be inherited from RawKeyring class

Author: Anirav Kareddy

src/main/java/software/amazon/encryption/s3/materials/AesKeyring.java

@@ -98,13 +98,6 @@ public EncryptionMaterials generateDataKey(EncryptionMaterials materials) {
             return defaultGenerateDataKey(materials);
         }
 
-        @Override
-        public EncryptionMaterials modifyMaterials(EncryptionMaterials materials) {
-            warnIfEncryptionContextIsPresent(materials);
-
-            return materials;
-        }
-
         @Override
         public byte[] encryptDataKey(SecureRandom secureRandom,
                 EncryptionMaterials materials)

src/main/java/software/amazon/encryption/s3/materials/RsaKeyring.java

@@ -103,13 +103,6 @@ public EncryptionMaterials generateDataKey(EncryptionMaterials materials) {
             return defaultGenerateDataKey(materials);
         }
 
-        @Override
-        public EncryptionMaterials modifyMaterials(EncryptionMaterials materials) {
-            warnIfEncryptionContextIsPresent(materials);
-
-            return materials;
-        }
-
         @Override
         public byte[] encryptDataKey(SecureRandom secureRandom,
                                      EncryptionMaterials materials) throws GeneralSecurityException {