Use colon instead of dot in header

Author: hollunder

doc/modules/http.websocket.md

@@ -53,7 +53,7 @@ The opcode `0x1` will be returned as `"text"` and `0x2` will be returned as `"bi
 
 Iterator over [`websocket:receive()`](#http.websocket:receive).
 
-#### Example {#http.websocket.each-example}
+#### Example {#http.websocket:each-example}
 
 ```lua
 local ws = websocket.new_from_uri("wss://echo.websocket.org")