[CrOS Settings] Re-enable OSSettingsFingerprintListTest.

Using the gn args in the reported failing build link and
repeating the test 100 times results in no errors.

Fixed: 1121139
Change-Id: Idce10ed5f31d60fcc3ecacf6dd49a2c6a624321b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2614850Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Commit-Queue: Regan Hsu <hsuregan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#842163}

chrome/test/data/webui/settings/chromeos/os_settings_browsertest.js

@@ -845,8 +845,7 @@ var OSSettingsFingerprintListTest = class extends OSSettingsBrowserTest {
   }
 };
 
-// TODO(https://crbug.com/1121139): Re-enable flaky test.
-TEST_F('OSSettingsFingerprintListTest', 'DISABLED_AllJsTests', () => {
+TEST_F('OSSettingsFingerprintListTest', 'AllJsTests', () => {
   mocha.run();
 });