[EG] reorder readme versions

[l0lawrence]

Remove system events from stable namespace api versions

Remove system events api versions from readme?? **

[openapi-pipeline-app]

Next Steps to Merge

Next steps that must be taken to merge this PR:

• ❌ This is the public specs repo main branch which is not intended for iterative development.
  You must acknowledge that you understand that after this PR is merged, you won't be able to stop your changes from being published to Azure customers.
  If this is what you intend, add PublishToCustomers label to your PR.
  Otherwise, retarget this PR onto a feature branch, i.e. with prefix release- (see aka.ms/azsdk/api-versions#release--branches).
• ❌ The required check named Automated merging requirements met has failed. This is the final check that must pass. Refer to the check in the PR's 'Checks' tab for details on how to fix it and consult the aka.ms/ci-fix guide. In addition, refer to step 4 in the PR workflow diagram

[openapi-pipeline-app]

Generated ApiView

Language	Package Name	ApiView Link
.Net	Azure.Messaging.EventGrid	There is no API change compared with the previous version

[l0lawrence]

I think these have to stay because swagger avocado check, can make a diff readme

[azure-sdk]

API change check

APIView has identified API level changes in this PR and created following API reviews.

Microsoft.EventGrid
Microsoft.EventGrid.SystemEvents