Make the open tabs sidebar snapshot focused on open tabs

Before this commit we had two very similar snapshots:
- interface-tabs-documentation-linux.png
- running-layout-documentation-linux.png

both showing "open tabs" and "kernels" sections.
After this commit the former now only shows "open tabs"
reducing the burden reviewing snapshots when kernels
are flaky or when kernels section changes

galata/test/documentation/overview.test.ts

@@ -31,21 +31,16 @@ test.describe('Overview', () => {
 
     await page.click('[title="Running Terminals and Kernels"]');
 
-    await page
-      .locator(
-        '.jp-RunningSessions-item.jp-mod-kernelspec >> text="Python 3 (ipykernel)"'
-      )
-      .waitFor();
-
-    // Freeze kernel ID
-    await page.evaluate(() => {
-      document.querySelector(
-        '.jp-RunningSessions-item-label-kernel-id'
-      ).innerText = '(abcd1234)';
-    });
+    // Close all other sections
+    const otherSections = page.locator(
+      '.jp-AccordionPanel-title.lm-mod-expanded:not([aria-label="Open Tabs Section"])'
+    );
+    for (const section of await otherSections.all()) {
+      await section.click();
+    }
 
     expect(
-      await page.screenshot({ clip: { y: 27, x: 0, width: 283, height: 400 } })
+      await page.screenshot({ clip: { y: 27, x: 0, width: 283, height: 200 } })
     ).toMatchSnapshot('interface_tabs.png');
   });