fix bug in pct calculation in memory usage alert

[Sohamdg081992]

PR Description

fix bug in pct calculation in memory usage alert.

I have deployed this fix for near ring clusters wcus and euseuap.

New Feature Checklist

• List telemetry added about the feature.
• Link to the one-pager about the feature.
• List any tasks necessary for release (3P docs, AKS RP chart changes, etc.) after merging the PR.
• Attach results of scale and perf testing.

Tests Checklist

• Have end-to-end Ginkgo tests been run on your cluster and passed? To bootstrap your cluster to run the tests, follow these instructions.
  • Labels used when running the tests on your cluster:
    • operator
    • windows
    • arm64
    • arc-extension
    • fips
• Have new tests been added? For features, have tests been added for this feature? For fixes, is there a test that could have caught this issue and could validate that the fix works?
  • Is a new scrape job needed?
    • The scrape job was added to the folder test-cluster-yamls in the correct configmap or as a CR.
  • Was a new test label added?
    • A string constant for the label was added to constants.go.
    • The label and description was added to the test README.
    • The label was added to this PR checklist.
    • The label was added as needed to testkube-test-crs.yaml.
  • Are additional API server permissions needed for the new tests?
    • These permissions have been added to api-server-permissions.yaml.
  • Was a new test suite (a new folder under /tests) added?
    • The new test suite is included in testkube-test-crs.yaml.