fix: improve copy for tasks "starting" page (#18247)

Update the copy on the task starting page to be more user-friendly:

- Change "Building the workspace" to "Starting your workspace"
- Change "Your task will run as soon as the workspace is ready" to "This
should take a few minutes"

The new copy provides clearer expectations about timing and uses more
user-friendly language.

Fixes #18164

Co-authored-by: blink-so[bot] <211532188+blink-so[bot]@users.noreply.github.com>

site/src/pages/TaskPage/TaskPage.tsx

@@ -92,10 +92,10 @@ const TaskPage = () => {
 				<div className="flex flex-col items-center">
 					<Spinner loading className="mb-4" />
 					<h3 className="m-0 font-medium text-content-primary text-base">
-						Building the workspace
+						Starting your workspace
 					</h3>
 					<span className="text-content-secondary text-sm">
-						Your task will run as soon as the workspace is ready
+						This should take a few minutes
 					</span>
 				</div>
 			</div>