Skip DevfileRegistriesList-related tests on non Kubernetes clusters

[rm3l]

What type of PR is this:
/kind bug
/area testing

What does this PR do / why we need it:
On Prow, users do not seem to have permission to install the DevfileRegistriesList Custom Resource Definition.

Which issue(s) this PR fixes:
Fixes #6637

PR acceptance criteria:

• Unit test

• Integration test

• Documentation

How to test changes / Special notes to the reviewer:
On an OpenShift cluster (with the oc client available in the PATH), this should pass:

unset KUBERNETES && make test-integration-cluster

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[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication

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[anandrkskd]

I will LGTM it as soon as the tests passes

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[odo-robot]

OpenShift Tests on commit finished with errors.
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[rm3l]

  Expected
      <*url.Error | 0xc0005f04e0>: {
          Op: "Post",
          URL: "http://127.0.0.1:33651/api/newuser",
          Err: <*errors.errorString | 0xc000070130>{s: "EOF"},
      }
  to be nil
  In [It] at: /go/odo_1/tests/e2escenarios/e2e_test.go:306

Summarizing 1 Failure:
  [FAIL] E2E Test starting with non-empty Directory add Binding [It] should verify developer workflow of using binding as env in innerloop
  /go/odo_1/tests/e2escenarios/e2e_test.go:306

Ran 7 of 7 Specs in 180.157 seconds
FAIL! -- 6 Passed | 1 Failed | 0 Pending | 0 Skipped

Flaky E2E test - reported in #6582

/override OpenShift-Integration-tests/OpenShift-Integration-tests

[openshift-ci]

@rm3l: Overrode contexts on behalf of rm3l: OpenShift-Integration-tests/OpenShift-Integration-tests

In response to this:

 Expected
     <*url.Error | 0xc0005f04e0>: {
         Op: "Post",
         URL: "http://127.0.0.1:33651/api/newuser",
         Err: <*errors.errorString | 0xc000070130>{s: "EOF"},
     }
 to be nil
 In [It] at: /go/odo_1/tests/e2escenarios/e2e_test.go:306

Summarizing 1 Failure:
 [FAIL] E2E Test starting with non-empty Directory add Binding [It] should verify developer workflow of using binding as env in innerloop
 /go/odo_1/tests/e2escenarios/e2e_test.go:306

Ran 7 of 7 Specs in 180.157 seconds
FAIL! -- 6 Passed | 1 Failed | 0 Pending | 0 Skipped

Flaky E2E test - reported in #6582

/override OpenShift-Integration-tests/OpenShift-Integration-tests

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[anandrkskd]

/lgtm

[anandrkskd]

/approve