Fix cosmos connection name in local.settings.json

[karstenjMSFT]

Issue describing the changes in this PR

The cosmos db extension samples expect the connection to be called CosmosDBConnection but in the local.settings.json file, it is specified as CosmosConnection. This fixes that.

Pull request checklist

• [ x] My changes do not require documentation changes
  • Otherwise: Documentation issue linked to PR
• [x ] My changes should not be added to the release notes for the next release
  • Otherwise: I've added my notes to release_notes.md
• [x ] My changes do not need to be backported to a previous version
  • Otherwise: Backport tracked by issue/PR #issue_or_pr
• I have added all required tests (Unit tests, E2E tests)
  This extension doesn't have any tests.

[kshyju]

Thank you @karstenjMSFT