remove v1alpha1 datadogagent examples

[celenechang]

What does this PR do?

Removes examples for deploying with v1alpha1 DatadogAgent manifests

Motivation

Cleanup as v1alpha1 is being deprecated.

Additional Notes

Anything else we should know when reviewing?

Minimum Agent Versions

Are there minimum versions of the Datadog Agent and/or Cluster Agent required?

• Agent: vX.Y.Z
• Cluster Agent: vX.Y.Z

Describe your test plan

Write there any instructions and details you may have to test your PR.

Checklist

• PR has at least one valid label: bug, enhancement, refactoring, documentation, tooling, and/or dependencies
• PR has a milestone or the qa/skip-qa label

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 54.87%. Comparing base (f14c8d4) to head (2abbf49).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1258   +/-   ##
=======================================
  Coverage   54.87%   54.87%           
=======================================
  Files         241      241           
  Lines       27893    27893           
=======================================
  Hits        15305    15305           
  Misses      11717    11717           
  Partials      871      871           

Flag	Coverage Δ
unittests	54.87% <ø> (ø)

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