Add the ARGOCD_ENV prefix in the helm with args example

[kroustou]

Description

The example that shows how avp can be invoked to render with the cm configmap has been updated to:

• include the added prefix in env vars (https://argocd-vault-plugin.readthedocs.io/en/stable/config/#argocd-240-environment-variable-prefix)
• respect the namespace of the application
  Fixes: <! -- link to issue -->

Checklist

Please make sure that your PR fulfills the following requirements:

• Reviewed the guidelines for contributing to this repository
• The commit message follows the Conventional Commits Guidelines.
• Tests for the changes have been updated
• Are you adding dependencies? If so, please run go mod tidy -compat=1.17 to ensure only the minimum is pulled in.
• Docs have been added / updated
• Optional. My organization is added to USERS.md.

Type of Change

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• New tests
• Build/CI related changes
• Documentation content changes
• Other (please describe)

Other information

[CLAassistant]

All committers have signed the CLA.

[codecov-commenter]

Codecov Report

Merging #431 (4a5deb8) into main (a71224e) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #431   +/-   ##
=======================================
  Coverage   77.17%   77.17%           
=======================================
  Files          23       23           
  Lines        1485     1485           
=======================================
  Hits         1146     1146           
  Misses        252      252           
  Partials       87       87           

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