Remove flag --experimental_remap_main_repo

It's on by default since Bazel 2.0, and the flag is now going away.

bazelbuild/bazel#7130
Signed-off-by: Laurent Le Brun <laurentlb@gmail.com>

.bazelrc

@@ -11,7 +11,6 @@
 startup --host_jvm_args=-Xmx2g
 
 build --workspace_status_command=bazel/get_workspace_status
-build --experimental_remap_main_repo
 build --experimental_local_memory_estimate
 build --experimental_strict_action_env=true
 build --host_force_python=PY2