Revert of Temporarily enable PlzNavigate to see perf bot results.

content/public/common/browser_side_navigation_policy.cc

Index: content/public/common/browser_side_navigation_policy.cc
diff --git a/content/public/common/browser_side_navigation_policy.cc b/content/public/common/browser_side_navigation_policy.cc
index aaf6f60fcb7c12f1232f21f485c1ba5f71e0c985..a94eff16cb802387a9ef9e44530eeb0dc0d947a1 100644
--- a/content/public/common/browser_side_navigation_policy.cc
+++ b/content/public/common/browser_side_navigation_policy.cc
@@ -10,7 +10,8 @@
 namespace content {
 
 bool IsBrowserSideNavigationEnabled() {
-  return true;
+  return base::CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kEnableBrowserSideNavigation);
 }
 
 }  // namespace content