fix(ziputil): ensure codeDiff is generated when there are uncommitted changes

[Hweinstock]

Problem

codeDiff folder was missing from zip output.

Solution

• optional parameter was not passed when it wasn't really optional.
• The source of this issue is addressed in refactor(ziputil): decouple ZipUtil from its consumers #6838 by avoiding these scopes entirely.

Verify

The following test case now passes when there are uncommitted changes to the repo.

// packages/core/src/test/codewhisperer/zipUtil.test.ts
it('should generate a codeDiff folder when there are uncommitted changes', async function () {
            const zipMetadata = await zipUtil.generateZip(vscode.Uri.file(appCodePath), CodeAnalysisScope.PROJECT)
            const zipFileData = await fs.readFileBytes(zipMetadata.zipFilePath)
            const zip = await JSZip.loadAsync(zipFileData)
            const files = Object.keys(zip.files)
            assert.ok(files.find((f) => f === ZipConstants.codeDiffFilePath))
}) 

I did not commit this test case because it fails when there are aren't uncommitted changes. Currently this is difficult to test due to the nature of the code. This partly addressed in the same PR above.

Future Work

Rework/refactor the gitdiff logic to be more testable.

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[github-actions]

• This pull request modifies code in src/* but no tests were added/updated.
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