chore(lex): update service name for lex runtime (#2424)

Author: raphkim

aws-android-sdk-core/src/main/java/com/amazonaws/internal/config/InternalConfig.java

@@ -118,7 +118,7 @@ private static Map<String, HttpClientConfig> getDefaultHttpClients() {
         ret.put("AWSKinesisVideoArchivedMediaClient", new HttpClientConfig("kinesisvideo"));
         ret.put("AWSKinesisVideoSignalingClient", new HttpClientConfig("kinesisvideo"));
         ret.put("AWSIotClient", new HttpClientConfig("execute-api"));
-        ret.put("AmazonLexRuntimeClient", new HttpClientConfig("runtime.lex"));
+        ret.put("AmazonLexRuntimeClient", new HttpClientConfig("lex"));
         ret.put("AmazonPinpointClient", new HttpClientConfig("mobiletargeting"));
         ret.put("AmazonPinpointAnalyticsClient", new HttpClientConfig("mobileanalytics"));
         //signer uses the servicename 'sagemaker' for Sagemaker Runtime
@@ -160,7 +160,7 @@ private static Map<String, SignerConfig> getDefaultServiceSigners() {
         ret.put("email", new SignerConfig("AWS4SignerType"));
         ret.put("s3", new SignerConfig("AWSS3V4SignerType"));
         ret.put("sdb", new SignerConfig("QueryStringSignerType"));
-        ret.put("runtime.lex", new SignerConfig("AmazonLexV4Signer"));
+        ret.put("lex", new SignerConfig("AmazonLexV4Signer"));
         ret.put("polly", new SignerConfig("AmazonPollyCustomPresigner"));
         return ret;
     }