NUT-19: fix link

Author: prusnak

19.md

@@ -29,7 +29,7 @@ The mint decides the `ttl` (Time To Live) of cached response, after which it can
 
 ## Settings
 
-Support for NUT-19 is announced as an extension to the `nuts` field of the `GetInfoResponse` described in [NUT-6](06).
+Support for NUT-19 is announced as an extension to the `nuts` field of the `GetInfoResponse` described in [NUT-06][06].
 
 The entry is structured as follows:
 
@@ -61,7 +61,4 @@ Where:
 
 If `ttl` is `null`, the responses are expected to be cached _indefinitely_.
 
-[03]: 03.md
-[04]: 04.md
-[05]: 05.md
 [06]: 06.md