chore: remove redundant GitHub Actions deployment workflows

Removed azure-deploy.yml and deploy.yml as all deployment automation
is now fully managed by Terraform ACR Task (see terraform/modules/azure/agentgateway/ci_cd.tf).

Kept the following workflows:
- release.yml: Builds releases for GHCR and creates GitHub releases
- pull_request.yml: CI validation (build, test, lint)
- e2e-tests.yml: E2E testing only

This ensures a single source of truth for deployment (Terraform) while
maintaining necessary CI/testing workflows.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: surinderunitone