Documentation/gitprotocol-v2.txt: fix a slight inconsistency in format

Signed-off-by: Xing Xin <xingxin.xx@bytedance.com>
Acked-by: Kristoffer Haugsbakk <kristofferhaugsbakk@fastmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: blanet

Documentation/gitprotocol-v2.txt

@@ -525,8 +525,8 @@ a request.
 
 The provided options must not contain a NUL or LF character.
 
- object-format
-~~~~~~~~~~~~~~~
+object-format
+~~~~~~~~~~~~~
 
 The server can advertise the `object-format` capability with a value `X` (in the
 form `object-format=X`) to notify the client that the server is able to deal