Removed the third_party flatbuffers, delete the link in manifest

Signed-off-by: Nzuojiangjiang <zuojiangjiang@huawei.com>

default.xml

@@ -264,7 +264,6 @@
   <project name="third_party_wayland_standard" path="third_party/wayland_standard"/>
   <project name="third_party_weston" path="third_party/weston"/>
   <project name="third_party_wpa_supplicant" path="third_party/wpa_supplicant"/>
-  <project name="third_party_flatbuffers" path="third_party/flatbuffers"/>
   <project name="third_party_pcre2" path="third_party/pcre2"/>
   <project name="third_party_selinux" path="third_party/selinux"/>
   <project name="third_party_gettext" path="third_party/gettext"/>