Bump bundled Quarto version (#6103)

Addresses #5643 by updating to the [current release
version](https://quarto.org/docs/download/) (not the pre-release).

Given that our tests don't run against the release build, I don't know
that we have anything to gain by running any specific tests here. I
_will_ kick off a release build for some manual spot checking.

We waited to do this because we do _not_ want this to go into this
month's Workbench patch release (Quarto's new Deno base), but we do
hope/expect this to land in the 2025.04 Workbench release.

### Release Notes

#### New Features

- Updated bundled Quarto to 1.6.40, the current release version

#### Bug Fixes

- N/A


### QA Notes

When this is in a release build, we should confirm that Quarto workflows
are all good to go!

build/lib/quarto.ts

@@ -89,7 +89,7 @@ function getQuartoLinux(version: string): Stream {
  */
 export function getQuartoStream(): Stream {
 	// quarto version
-	const version = '1.5.55';
+	const version = '1.6.40';
 
 	fancyLog(`Synchronizing quarto ${version}...`);