Revert of Temporarily enable PlzNavigate to see perf bot results. (patchset #1...

Revert of Temporarily enable PlzNavigate to see perf bot results. (patchset #1 id:1 of https://codereview.chromium.org/2584093003/ )

Reason for revert:
Change cycled to perf bots.

Original issue's description:
> Temporarily enable PlzNavigate to see perf bot results.
>
> BUG=368813
> TBR=clamy@chromium.org
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
>
> Committed: https://chromium.googlesource.com/chromium/src/+/3d001c287618b8298e5b95bd98556a5beffc0316
> Committed: https://crrev.com/722be6f390eba4c47669ad4307d2580dc09762dc
> Cr-Commit-Position: refs/heads/master@{#439731}

TBR=clamy@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=368813

Review-Url: https://codereview.chromium.org/2587333002
Cr-Commit-Position: refs/heads/master@{#439732}

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