Revert "WebUI: Remove WebUIA11yEnhancements flag"

This reverts commit 4fa625ab16bd89a86f99673e9f1b897fe0314b5a.

Reason for revert: Likely culprit for failure "$i18n replacement key "a11yenhanced" not found"

Failing bot: https://ci.chromium.org/p/chromium/builders/ci/linux-chromeos-dbg

First instance: https://ci.chromium.org/p/chromium/builders/ci/linux-chromeos-dbg/18639

Original change's description:
> WebUI: Remove WebUIA11yEnhancements flag
> 
> Bug: 1067718
> Change-Id: I74ea1117ba515531cac9e0d308163f97eb28e9f3
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2186077
> Reviewed-by: Esmael Elmoslimany <[email protected]>
> Reviewed-by: Scott Violet <[email protected]>
> Commit-Queue: John Lee <[email protected]>
> Cr-Commit-Position: refs/heads/master@{#767900}

[email protected],[email protected],[email protected]

Change-Id: I2e1f5bd6edf2e4c04b189081fda701c4249ac710
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1067718
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2197819
Reviewed-by: Connie Wan <[email protected]>
Commit-Queue: Connie Wan <[email protected]>
Cr-Commit-Position: refs/heads/master@{#768022}
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index acad1df..c74a891d 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -3654,6 +3654,10 @@
     {"ntp-webui", flag_descriptions::kNtpWebUIName,
      flag_descriptions::kNtpWebUIDescription, kOsDesktop,
      FEATURE_VALUE_TYPE(ntp_features::kWebUI)},
+
+    {"webui-a11y-enhancements", flag_descriptions::kWebUIA11yEnhancementsName,
+     flag_descriptions::kWebUIA11yEnhancementsDescription, kOsDesktop,
+     FEATURE_VALUE_TYPE(features::kWebUIA11yEnhancements)},
 #endif  // !defined(OS_ANDROID)
 
 #if defined(DCHECK_IS_CONFIGURABLE)