schema/fs: Drop *.go files

With:

  $ go get -u github.com/mjibson/esc
  $ make schema/fs.go

now that 6f633c2 (schema/gen: Include .json instead of excluding .go,
2017-01-27, opencontainers#538) has landed.

Signed-off-by: W. Trevor King <[email protected]>

Author: wking