S3 remote state use application/json Content-Type.

The state is always JSON, in spite of the fact that this interface
presents it as an opaque byte array. It's more helpful to those interacting
with the state object outside of Terraform for it to have a more specific
content-type.

state/remote/s3.go

@@ -133,7 +133,7 @@ func (c *S3Client) Get() (*Payload, error) {
 }
 
 func (c *S3Client) Put(data []byte) error {
-	contentType := "application/octet-stream"
+	contentType := "application/json"
 	contentLength := int64(len(data))
 
 	i := &s3.PutObjectInput{