doc: gitprotocol-pack: fix pronoun-antecedent agreement

Fix "pronoun-antecedent agreement" errors.

Signed-off-by: LorenzoPegorari <lorenzo.pegorari2002@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: LorenzoPegorari

Documentation/gitprotocol-pack.adoc

@@ -65,7 +65,7 @@ Extra Parameters
 ----------------
 
 The protocol provides a mechanism in which clients can send additional
-information in its first message to the server. These are called "Extra
+information in their first message to the server. These are called "Extra
 Parameters", and are supported by the Git, SSH, and HTTP protocols.
 
 Each Extra Parameter takes the form of `<key>=<value>` or `<key>`.
@@ -277,7 +277,7 @@ out of what the server said it could do with the first 'want' line.
   filter-request    =  PKT-LINE("filter" SP filter-spec)
 ----
 
-Clients MUST send all the obj-ids it wants from the reference
+Clients MUST send all the obj-ids they want from the reference
 discovery phase as 'want' lines. Clients MUST send at least one
 'want' command in the request body. Clients MUST NOT mention an
 obj-id in a 'want' command which did not appear in the response