rename env-variable PORT to WEBHOOK_PORT

[sergkondr]

Fixes #127

Description
Change env variable PORT -> WEBHOOK_PORT as it is described in the docs

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[ellistarn]

Nice catch! Looking at our helm chart, it's definitely WebhookPort

[coveralls]

Pull Request Test Coverage Report for Build 3676205689

• 0 of 1 (0.0%) changed or added relevant line in 1 file are covered.
• 6 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.05%) to 75.944%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/operator/options/options.go	0	1	0.0%

Files with Coverage Reduction	New Missed Lines	%
pkg/scheduling/requirements.go	2	98.5%
pkg/controllers/node/controller.go	4	59.7%

Totals
Change from base Build 3660279282:	-0.05%
Covered Lines:	5550
Relevant Lines:	7308

---

💛 - Coveralls

[sergkondr]

@ellistarn thank you! And thank you for such a lovely thing like Karpenter :)
Do I have to do something with this pull request to ensure it is good enough to be merged?

[ellistarn]

@ellistarn thank you! And thank you for such a lovely thing like Karpenter :)
Do I have to do something with this pull request to ensure it is good enough to be merged?

Nope you're good. Looks like github actions is on holiday -- that last job won't report.