protocol-caps.h: add newline at end of file

Add a trailing newline to the protocol-caps.h file added in the recent
a2ba162cda (object-info: support for retrieving object info,
2021-04-20). Various editors add this implicitly, and some compilers
warn about the lack of a \n here.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

protocol-caps.h

@@ -7,4 +7,4 @@ struct packet_reader;
 int cap_object_info(struct repository *r, struct strvec *keys,
 		    struct packet_reader *request);
 
-#endif /* PROTOCOL_CAPS_H */
+#endif /* PROTOCOL_CAPS_H */