[fuchsia-pkg][cmx_schema] Remove deprecated-bare-pkg-url

Now that deprecated-bare-package-url is merged in at build time in GN
with a build flag, but *after* cmx validation, we can get rid of this.
This prevents developers from manually adding the flag to their cmx
files.

Possible concerns:
- missed cases during flag flip, one less possible hot fix path.
- google3/outside of GN don't have cmx valildation (check with dgonyeo);
  if they have, then we'd need to keep an eye on that copy of the schema.

TESTED=fx set x64; fx full-build

CF-156 #comment

Change-Id: I68851d46b1af2a7b50d07f1797ca042b66e628a9
1 file changed