test: update vscode-lm-format test to match new image placeholder format

Author: roomote

src/api/transform/__tests__/vscode-lm-format.spec.ts

@@ -170,7 +170,7 @@ describe("convertToVsCodeLmMessages", () => {
 
 		expect(result).toHaveLength(1)
 		const imagePlaceholder = result[0].content[1] as MockLanguageModelTextPart
-		expect(imagePlaceholder.value).toContain("[Image (base64): image/png not supported by VSCode LM API]")
+		expect(imagePlaceholder.value).toContain("[Image (base64): image/png]")
 	})
 })