Remove old code in DarkModeImageClassifier.

After crrev.com/c/2352251, the code added for storing cache result
after doing initial classification, is not required. This patch
removes it.

Bug: 1094005
Change-Id: I010bfeba0d97e9360482a57ba83bae43e178c88e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2364383Reviewed-by: Fredrik Söderquist <fs@opera.com>
Reviewed-by: Stephen Chenney <schenney@chromium.org>
Commit-Queue: Prashant Nevase <prashant.n@samsung.com>
Cr-Commit-Position: refs/heads/master@{#800286}

third_party/blink/renderer/platform/graphics/dark_mode_image_classifier.cc

@@ -117,11 +117,6 @@ DarkModeClassification DarkModeImageClassifier::Classify(
   if (result != DarkModeClassification::kNotClassified)
     return result;
 
-  if (result != DarkModeClassification::kNotClassified) {
-    cache->Add(image_id, src, result);
-    return result;
-  }
-
   auto features_or_null = GetFeatures(paint_image, src);
   if (!features_or_null) {
     // Do not cache this classification.