Update GCE.md
Update GCE.md

Former-commit-id: 9cd1fff7159b8cc4ed590323b4519adf4a0bb6d9
TrimBiggs/libnetwork-plugin,caseydavenport/libcalico,djosborne/libcalico,projectcalico/libnetwork-plugin,tomdee/libnetwork-plugin,TrimBiggs/libnetwork-plugin,plwhite/libcalico,projectcalico/libcalico,alexhersh/libcalico,tomdee/libcalico,Symmetric/libcalico,TrimBiggs/libcalico,insequent/libcalico,robbrockbank/libcalico,L-MA/libcalico