[VS Code] Update verbiage on Diagnostics settings section

Problem to solve

When meeting with @mcorren, I realized the language surrounding where the settings section in the Diangostics comes from is not clear.

Currently the settings section shows only non-default settings related to the GitLab Workflow extension:

### JSON Settings

These are settings combined from your global `settings.json` and project-specific `settings.json`:

```json
{
  "gitlab.duoCodeSuggestions.additionalLanguages": [
    "html",
    "Markdown"
  ],
  "gitlab.debug": true,
  "gitlab.ca": ""
}

The phrasing:

These are settings combined from your global settings.json and project-specific settings.json:

does not indicate that the settings here are only those that are not default.

Proposal

Update the phrasing to more clearly indicate that these are NOT all the settings and just the ones that differ from the default.

Further details

Links / references