fix: remove X- prefix from header names

0014-http-ilp/0014-http-ilp.md

@@ -140,7 +140,7 @@ The paid HTTP request is fired off:
 ``` http
 POST /upload HTTP/1.1
 Host: myservice.example
-X-Pay-Token: 7y0SfeN7lCuq0GFF5UsMYZofIjJ7LrvPvsePVWSv450
+Pay-Token: 7y0SfeN7lCuq0GFF5UsMYZofIjJ7LrvPvsePVWSv450
 ```
 ```
 [...]
@@ -154,8 +154,8 @@ The server returns an HTTP error of `402 Payment Required` and includes response
 
 ``` http
 HTTP/1.1 402 Payment Required
-X-Pay: 10 us.nexus.ankita.~recv.filepay SkTcFTZCBKgP6A6QOUVcwWCCgYIP4rJPHlIzreavHdU
-X-Pay-Balance: 0
+Pay: 10 us.nexus.ankita.~recv.filepay SkTcFTZCBKgP6A6QOUVcwWCCgYIP4rJPHlIzreavHdU
+Pay-Balance: 0
 ```
 
 The client may use the condition seed to create a condition to pay this host. The condition seed is generated by the server as follows:
@@ -232,7 +232,7 @@ Once the HTTP-ILP client module receives the fulfillment, it will now retry its
 ``` http
 POST /upload HTTP/1.1
 Host: myservice.example
-X-Pay-Token: 7y0SfeN7lCuq0GFF5UsMYZofIjJ7LrvPvsePVWSv450
+Pay-Token: 7y0SfeN7lCuq0GFF5UsMYZofIjJ7LrvPvsePVWSv450
 ```
 ```
 [...]
@@ -242,8 +242,8 @@ This time, the request succeeds:
 
 ``` http
 HTTP/1.1 200 OK
-X-Pay: 10 us.nexus.ankita.~recv.filepay SkTcFTZCBKgP6A6QOUVcwWCCgYIP4rJPHlIzreavHdU
-X-Pay-Balance: 90
+Pay: 10 us.nexus.ankita.~recv.filepay SkTcFTZCBKgP6A6QOUVcwWCCgYIP4rJPHlIzreavHdU
+Pay-Balance: 90
 ```
 
 Notice how the 100 units credit from the payment was added to the balance and the 10 unit cost for the current request was subtracted.