fix: missing z character

Co-authored-by: Vladimír Gorej <[email protected]>

Author: baywet

src/oas.md

@@ -562,7 +562,7 @@ The server URL templating is defined by the following [ABNF](https://tools.ietf.
 ```abnf
 server-url-template  = 1*( literals / server-variable )
 server-variable      = "{" server-variable-name "}"
-server-variable-name = 1*( %x00-79 / %x7C / %x7E-10FFFF ) ; every UTF8 character except { and }
+server-variable-name = 1*( %x00-7A / %x7C / %x7E-10FFFF ) ; every UTF8 character except { and }
 
 literals       = 1*( %x21 / %x23-24 / %x26-3B / %x3D / %x3F-5B
                / %x5D / %x5F / %x61-7A / %x7E / ucschar / iprivate