Fix missing return value

Author: billrobertson42

aws-serverless-java-container-core/src/main/java/com/amazonaws/serverless/proxy/internal/servlet/AwsProxyHttpServletResponseWriter.java

@@ -64,7 +64,7 @@ private boolean isBinary(String contentType) {
                 return LambdaContainerHandler.getContainerConfig().isBinaryContentType(contentType.substring(0, semidx));
             }
             else {
-                LambdaContainerHandler.getContainerConfig().isBinaryContentType(contentType);
+                return LambdaContainerHandler.getContainerConfig().isBinaryContentType(contentType);
             }
         }
         return false;