Remove unused feature flag

This feature flag is duplicated in previews_features.h and wasn't
being referenced in code or tests.

Change-Id: Iffe553bc9359f03745814416cabb1c0d2bdbe0fe
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1845967
Auto-Submit: Sophie Chang <sophiechang@chromium.org>
Reviewed-by: Doug Arnett <dougarnett@chromium.org>
Commit-Queue: Sophie Chang <sophiechang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#703922}

components/optimization_guide/optimization_guide_features.cc

@@ -41,10 +41,6 @@ const base::Feature kOptimizationHints {
 const base::Feature kOptimizationHintsExperiments{
     "OptimizationHintsExperiments", base::FEATURE_DISABLED_BY_DEFAULT};
 
-// Provides slow page triggering parameters.
-const base::Feature kSlowPageTriggering{"PreviewsSlowPageTriggering",
-                                        base::FEATURE_DISABLED_BY_DEFAULT};
-
 // Enables fetching optimization hints from a remote Optimization Guide Service.
 const base::Feature kOptimizationHintsFetching{
     "OptimizationHintsFetching", base::FEATURE_DISABLED_BY_DEFAULT};

components/optimization_guide/optimization_guide_features.h

@@ -20,7 +20,6 @@ namespace features {
 extern const base::Feature kOptimizationHints;
 extern const base::Feature kOptimizationHintsExperiments;
 constexpr char kOptimizationHintsExperimentNameParam[] = "experiment_name";
-extern const base::Feature kSlowPageTriggering;
 extern const base::Feature kOptimizationHintsFetching;
 extern const base::Feature kOptimizationGuideKeyedService;