fix js lint let -> const

Author: guspower

tests/end-to-end/official-site.spec.ts

@@ -159,8 +159,8 @@ test("no console errors on card page", async ({ page }) => {
 });
 
 test("CSP issues unique nonces per request", async ({page}) => {
-  let csp1 = await (await page.goto(BASE)).headerValue("content-security-policy");
-  let csp2 = await (await page.reload()).headerValue("content-security-policy");
+  const csp1 = await (await page.goto(BASE)).headerValue("content-security-policy");
+  const csp2 = await (await page.reload()).headerValue("content-security-policy");
 
   expect(csp1, `check if ${csp1} != ${csp2}`).not.toEqual(csp2);
 });