Avoid conflict with the VERSION build arg

[guicassolato]

Use a different name for the VERSION build arg in the Dockerfile, to avoid conflict with env vars set at the base image.

❯ docker run --rm -ti registry.access.redhat.com/ubi9/go-toolset:1.21 /bin/bash
bash-5.1$ echo ${VERSION}
1.21.13

[codecov-commenter]

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Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 61.78%. Comparing base (b9f6460) to head (98e962a).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #217 +/- ## ======================================= Coverage 61.78% 61.78% ======================================= Files 2 2 Lines 785 785 ======================================= Hits 485 485 Misses 249 249 Partials 51 51 ``` | [Flag](https://app.codecov.io/gh/Kuadrant/authorino-operator/pull/217/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Kuadrant) | Coverage Δ | | |---|---|---| | [unit](https://app.codecov.io/gh/Kuadrant/authorino-operator/pull/217/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Kuadrant) | `61.78% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Kuadrant#carryforward-flags-in-the-pull-request-comment) to find out more.

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