Upgrade main chart version to 2.0.0

[bugraoz93]

• This will be reflected also in kustomize tests, which version has been tested with, related: Smoke test kustomize overlays and add tested Kerberos #67012

Related consensus: https://lists.apache.org/thread/rzp4n3dj2bcyg6mm18h6cc20bhbc07h6
Related Confluence page: https://cwiki.apache.org/confluence/display/AIRFLOW/Direction+and+Plan+for+Chart+2.0

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• Read the Pull Request Guidelines for more information. Note: commit author/co-author name and email in commits become permanently public when merged.
• For fundamental code changes, an Airflow Improvement Proposal (AIP) is needed.
• When adding dependency, check compliance with the ASF 3rd Party License Policy.
• For significant user-facing changes create newsfragment: {pr_number}.significant.rst, in airflow-core/newsfragments. You can add this file in a follow-up commit after the PR is created so you know the PR number.

[bugraoz93]

cc: @Miretpl and @wolfdn