Reduce flakiness of CPU calibration test

According to flaky test history[1], the primary failure mode was CI
machines being too slow to calibrate the mid-tier device.

[1] https://tinyurl.com/yc6etpjx

Bug: 311438112
Change-Id: Iac905fcb6f4f0a12599036f4f62271462311091b
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/6265743
Auto-Submit: Connor Clark <[email protected]>
Commit-Queue: Connor Clark <[email protected]>
Commit-Queue: Paul Irish <[email protected]>
Reviewed-by: Paul Irish <[email protected]>

Author: Connor Clark

test/e2e/throttling/cpu_calibration_test.ts

@@ -25,8 +25,9 @@ describe('CPU Calibration', () => {
     await click('.calibrate-button');
     await waitForElementWithTextContent('Recalibrate');
 
+    // Verify that at least the low-tier device was able to be calibrated (CI may be to slow for mid-tier calibration).
     const results = await getAllTextContents('.cpu-preset-result');
     assert.include(results[0], 'slowdown');
-    assert.include(results[1], 'slowdown');
+    assert.match(results[1] ?? '', /slowdown|not powerful enough/);
   });
 });