Fix empty readiness probe failures for Knative

[halim-lee]

What this PR does / why we need it?:

• Fixes empty readiness probe failures for Knative
• Removes unsetting port and unsets scheme

Does this PR introduce a user-facing change?

• User guide
• CHANGELOG.md

Which issue(s) this PR fixes:

WASdev/websphere-liberty-operator#400

[halim-lee]

If HTTPGet.Scheme is not set to be empty, the code uses our default readiness probe configurations in https://github.com/application-stacks/runtime-component-operator/blob/main/common/common.go#L25-L39. This sets HTTPGet.Scheme to be HTTPS, which is not supported by Knative at the moment.
When HTTPGet.Scheme is set to "", Knative automatically updates it to HTTP. And Knative service reconciles properly.

With resetting HTTPGet.Scheme to "":

KSVC:
          readinessProbe:
            failureThreshold: 10
            httpGet:
              path: /health/ready
              port: 9080
            initialDelaySeconds: 10
            periodSeconds: 10
            successThreshold: 1
            timeoutSeconds: 2

Pod:
            - name: SERVING_READINESS_PROBE
              value: '{"httpGet":{"path":"/health/ready","port":9080,"host":"127.0.0.1","scheme":"HTTP"},"initialDelaySeconds":10,"timeoutSeconds":2,"periodSeconds":10,"successThreshold":1,"failureThreshold":10}'

Without resetting HTTPGet.Scheme to "":

KSVC:
          readinessProbe:
            failureThreshold: 10
            httpGet:
              path: /health/ready
              port: 0
              scheme: HTTPS
            initialDelaySeconds: 10
            periodSeconds: 10
            successThreshold: 1
            timeoutSeconds: 2

Pod:
        - name: SERVING_READINESS_PROBE
          value: '{"httpGet":{"path":"/health/ready","port":9080,"host":"127.0.0.1","scheme":"HTTPS"},"initialDelaySeconds":10,"timeoutSeconds":2,"periodSeconds":10,"successThreshold":1,"failureThreshold":10}'