docs: Remove stale update.sh, upgrade.sh, and reconciliation references

[ngjinshan]

Thorough cleanup of all documentation to reflect current state:

• INSTRUCTIONS.md: replace update.sh flow with CloudShell commands
• OVERVIEW.md: remove reconciliation from components/cost tables, replace update.sh references with CloudShell workflow
• LIMITATIONS.md: remove reconciliation VPC scope section (no longer applicable since reconciliation was removed)
• README.md: remove reconciliation from cost table
• VERSIONING.md: remove upgrade.sh references
• DEVELOPMENT.md: mark editor/upgrade flows as disabled

CHANGELOG.md left untouched (historical record).

Description

Brief description of the change and the problem it solves.

Type of change

• Bug fix
• New resource type support
• Security improvement
• Documentation update

Testing

• Tested end-to-end in a real AWS account (or CI E2E will cover this)
• No false positives observed
• CloudWatch logs reviewed for errors

Checklist

• CloudFormation template is valid (cfn-lint passes — checked by CI)
• IAM permissions follow least-privilege (only tag actions added)
• If adding a new service handler: corresponding resource added to .github/scripts/resource_groups/ for E2E coverage
• CHANGELOG.md updated

CI Notes

Layer 1 (lint) runs immediately on every PR — ~1 min.
Layer 2 (E2E) runs when configurator.yaml or configurator.html changes — ~37 min across 7 AWS accounts. No AWS credentials needed.
If Layer 2 fails, download verification-report.json from the Actions run for details.