Remove unused feedback switches for Reader Mode.

Bug: 982354
Change-Id: Ia10914a769bda850027bd8c5206f477aac2141ef
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1775099Reviewed-by: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Commit-Queue: Aran Gilman <gilmanmh@google.com>
Cr-Commit-Position: refs/heads/master@{#692133}

components/dom_distiller/core/dom_distiller_switches.cc

@@ -19,9 +19,4 @@ const char kAlwaysTrue[] = "alwaystrue";
 const char kNone[] = "none";
 }  // namespace reader_mode_heuristics
 
-namespace reader_mode_feedback {
-const char kOn[] = "on";
-const char kOff[] = "off";
-}  // namespace reader_mode_feedback
-
 }  // namespace switches

components/dom_distiller/core/dom_distiller_switches.h

@@ -30,11 +30,6 @@ extern const char kAlwaysTrue[];
 extern const char kNone[];
 }  // namespace reader_mode_heuristics
 
-namespace reader_mode_feedback {
-extern const char kOn[];
-extern const char kOff[];
-}  // namespace reader_mode_feedback
-
 }  // namespace switches
 
 #endif  // COMPONENTS_DOM_DISTILLER_CORE_DOM_DISTILLER_SWITCHES_H_