docs(knapsack): edit the target for change event to cv-checkbox

[bsahitya]

Description

Edit the target field for change event of checkbox component to 'cv-checkbox'

Test Steps

• [x] Run the start command for knapsack from nx console
• [x] Open the localhost url
• [x] Verify the changes

General Tests for Every PR

• [x] npm run start still works.
• [x] npm run lint passes.
• [x] npm run stylelint passes.
• [x] npm test passes and code coverage is not lower.
• [x] npm run build still works.

Screenshots

[owilliams320]

:tada: This PR is included in version 8.6.0 :tada:

The release is available on:

• v8.6.0
• GitHub release

Your semantic-release bot :package::rocket: