fix: KUBECONFIG gets set when using --kubeconfig via var DEVSPACE_FLAGS

[siredmar]

What issue type does this pull request address? (keep at least one, remove the others)
/kind bugfix

What does this pull request do? Which issues does it resolve? (use resolves #<issue_number> if possible)
resolves #2859

Please provide a short message that should be published in the DevSpace release notes
Environment variable KUBECONFIG gets set when using --kubeconfig via variable DEVSPACE_FLAGS within devspace.yaml

What else do we need to know?

[netlify]

✅ Deploy Preview for devspace-docs canceled.

Built without sensitive environment variables

Name	Link
🔨 Latest commit	d8978ac
🔍 Latest deploy log	https://app.netlify.com/sites/devspace-docs/deploys/66eadf184d58890007fa84d1

[siredmar]

@FabianKramm, @LukasGentele would any of you guys mind reviewing this?

[lizardruss]

@siredmar Can you take a look at the e2e test failures?

[siredmar]

@lizardruss

TL;DR Would you mind re-running the pipeline?

The failing e2e test seems like a problem with the OCI registry. Not sure if this is actually related to my change as both e2e tests for k8s 1.27.3 and 1.28.0 fail with the same error in different test cases both at exactly the same time (18:21:11).
https://github.com/devspace-sh/devspace/actions/runs/9282659759/job/26246098358?pr=2860#step:8:5178
https://github.com/devspace-sh/devspace/actions/runs/9282659759/job/26246097543?pr=2860#step:8:3116

[siredmar]

@lizardruss please trigger a re-run of the e2e tests. Thanks.

[lizardruss]

Unsure why linting suddenly fails, but I can address those in a separate PR.