puppeteer_test: Add waitForNavigation when reloading.

This commit ensures that it waits until the
page is reloaded which avoids uncertain
flake.

frontend_tests/puppeteer_tests/07-navigation.ts

@@ -58,6 +58,7 @@ async function test_reload_hash(page: Page): Promise<void> {
     const initial_hash = await page.evaluate(() => window.location.hash);
 
     await page.evaluate(() => zulip_test.initiate_reload({immediate: true}));
+    await page.waitForNavigation();
     await page.waitForSelector("#zfilt", {visible: true});
 
     const page_load_time = await page.evaluate(() => page_params.page_load_time);