build: reorder PACKAGE_GROUP entries to make @angular/core the first one

[IgorMinar]

CLI will soon consider the first entry to be the main entry in the package group.

This will then be used to display the main entry in "ng update" listing.

//cc: @hansl

[hansl]

Nit; add a comment so that when adding packages someone doesn’t change the order by mistake (since it looks alphabetical).

[IgorMinar]

done

[alexeagle]

Note that if we use buildifier at some point to format this file, it has a # do not sort comment (see other BAZEL.build files)
I'm surprised that CLI has this behavior (why would it should users @angular/core to mean all @angular packages?) but it's out of scope here

[ngbot]

I see that you just added the PR action: merge label, but the following checks are still failing:
     forbidden label detected: PR action: review
     status "continuous-integration/travis-ci/pr" is failing

If you want your PR to be merged, it has to pass all the CI checks.

If you can't get the PR to a green state due to flakes or broken master, please try rebasing to master and/or restarting the CI job. If that fails and you believe that the issue is not due to your change, please contact the caretaker and ask for help.

[angular-automatic-lock-bot]

This issue has been automatically locked due to inactivity.
Please file a new issue if you are encountering a similar or related problem.

Read more about our automatic conversation locking policy.

_{This action has been performed automatically by a bot.}