Remove netcat from the manifest.

toybox supplies netcat now.
Bug: N/A
Test: builds
Change-Id: Ia4c004d403eda4240ffe9c8ea248002efeed008e

default.xml

@@ -263,7 +263,6 @@
   <project path="external/nanohttpd" name="platform/external/nanohttpd" groups="pdk" />
   <project path="external/nanopb-c" name="platform/external/nanopb-c" groups="pdk" />
   <project path="external/naver-fonts" name="platform/external/naver-fonts" groups="pdk" />
-  <project path="external/netcat" name="platform/external/netcat" groups="pdk" />
   <project path="external/neven" name="platform/external/neven" groups="pdk" />
   <project path="external/nfacct" name="platform/external/nfacct" groups="pdk" />
   <project path="external/nist-pkits" name="platform/external/nist-pkits" groups="pdk" />