Remove net/interfaces.

All it has is an OWNERS file, left over from
https://chromium-review.googlesource.com/c/chromium/src/+/1323791

Bug: 901419
Change-Id: Ifc6989523ffb102f4aa9f98d2d7c0c58c5e4971d
Reviewed-on: https://chromium-review.googlesource.com/c/1340524Reviewed-by: Eric Roman <eroman@chromium.org>
Commit-Queue: Matt Menke <mmenke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609063}

net/interfaces/OWNERS

-per-file *.mojom=set noparent
-per-file *.mojom=file://ipc/SECURITY_OWNERS
-per-file *_struct_traits*.*=set noparent
-per-file *_struct_traits*.*=file://ipc/SECURITY_OWNERS
-per-file *.typemap=set noparent
-per-file *.typemap=file://ipc/SECURITY_OWNERS
-per-file *_mojom_traits*.*=set noparent
-per-file *_mojom_traits*.*=file://ipc/SECURITY_OWNERS