fix(sdk) separator param. Part of #791

[Udiknedormin]

Which issue is resolved by this Pull Request:
A fix to the previous partial solution (PR #837) of #791.

Description of your changes:
Remove separator field from params inside of the loop spec. Separator shouldn't be available inside of the spec.

As noted by Tommy Li in PR #838 for range-loop support, and as confirmed by checking the PipelineLoop test for text-separator:

var aPipeline = &v1beta1.Pipeline{
	ObjectMeta: metav1.ObjectMeta{Name: "a-pipeline", Namespace: "foo"},
	Spec: v1beta1.PipelineSpec{
		Params: []v1beta1.ParamSpec{{
			Name: "current-item",
			Type: v1beta1.ParamTypeString,
		}, {
			Name: "additional-parameter",
			Type: v1beta1.ParamTypeString,
		}},
		Tasks: []v1beta1.PipelineTask{{
			Name: "mytask",
			TaskSpec: &v1beta1.EmbeddedTask{
				TaskSpec: v1beta1.TaskSpec{
					Steps: []v1beta1.Step{{
						Container: corev1.Container{Name: "foo", Image: "bar"},
					}},
				},
			},
		}},
	},
}

var aPipelineLoop = &pipelineloopv1alpha1.PipelineLoop{
	ObjectMeta: metav1.ObjectMeta{Name: "a-pipelineloop", Namespace: "foo"},
	Spec: pipelineloopv1alpha1.PipelineLoopSpec{
		PipelineRef:           &v1beta1.PipelineRef{Name: "a-pipeline"},
		IterateParam:          "current-item",
		IterateParamSeparator: "separator",
	},
}

...the param is absent in the pipeline spec, despite being there in the custom task call:

var runPipelineLoopWithInStringSeparatorParams = &v1alpha1.Run{
	ObjectMeta: metav1.ObjectMeta{
		Name:      "run-pipelineloop",
		Namespace: "foo",
		Labels: map[string]string{
			"myTestLabel":                    "myTestLabelValue",
			"custom.tekton.dev/pipelineLoop": "a-pipelineloop",
			"tekton.dev/pipeline":            "pr-loop-example",
			"tekton.dev/pipelineRun":         "pr-loop-example",
			"tekton.dev/pipelineTask":        "loop-task",
		},
		Annotations: map[string]string{
			"myTestAnnotation": "myTestAnnotationValue",
		},
	},
	Spec: v1alpha1.RunSpec{
		Params: []v1beta1.Param{{
			Name:  "current-item",
			Value: v1beta1.ArrayOrString{Type: v1beta1.ParamTypeString, StringVal: "item1|item2"},
		}, {
			Name:  "separator",
			Value: v1beta1.ArrayOrString{Type: v1beta1.ParamTypeString, StringVal: "|"},
		}, {
			Name:  "additional-parameter",
			Value: v1beta1.ArrayOrString{Type: v1beta1.ParamTypeString, StringVal: "stuff"},
		}},
		Ref: &v1alpha1.TaskRef{
			APIVersion: pipelineloopv1alpha1.SchemeGroupVersion.String(),
			Kind:       pipelineloop.PipelineLoopControllerName,
			Name:       "a-pipelineloop",
		},
	},
}

So this PR removes that param from pipeline spec inside of the loop.

Environment tested:

• Python Version (use python --version): python 3.9
• Tekton Version (use tkn version): irrelevant
• Kubernetes Version (use kubectl version): irrelevant
• OS (e.g. from /etc/os-release): irrelevant

Checklist:

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[Tomcli]

/lgtm
/approve

[google-oss-prow]

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This pull-request has been approved by: Tomcli, Udiknedormin

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