removed unused import

Author: Anirav Kareddy

src/main/java/software/amazon/encryption/s3/internal/ContentMetadataDecodingStrategy.java

@@ -23,7 +23,6 @@
 import java.util.Base64;
 import java.util.HashMap;
 import java.util.Map;
-import java.util.Optional;
 import java.util.concurrent.CompletionException;
 
 import static software.amazon.encryption.s3.S3EncryptionClientUtilities.INSTRUCTION_FILE_SUFFIX;