Require dependency & remove unneeded check

Author: hieuwu

pom.xml

@@ -75,7 +75,6 @@
       <groupId>software.amazon.awssdk</groupId>
       <artifactId>kms</artifactId>
       <version>2.28.28</version>
-      <optional>true</optional>
     </dependency>
 
     <!-- Used when enableMultipartPutObject is configured -->

src/main/java/software/amazon/encryption/s3/S3EncryptionClient.java

@@ -1139,11 +1139,6 @@ public S3EncryptionClient build() {
                             .secureRandom(_secureRandom)
                             .build();
                 } else if (_kmsKeyId != null) {
-                    try {
-                        Class.forName("software.amazon.awssdk.services.kms.KmsClient");
-                    } catch (ClassNotFoundException e) {
-                        throw new RuntimeException("software.amazon.awssdk:kms is required to set up with KMS key", e);
-                    }
                     KmsClient kmsClient = KmsClient.builder()
                             .credentialsProvider(_awsCredentialsProvider)
                             .region(_region)