Revert "Add namespace sandbox to about page."

Revert "Add namespace sandbox to about page."

Reason for revert:
See crbug/456993.

This reverts commit 1ef7ee1ee899087d8632a4f905a3a11697a20b81.

TBR=jln,jhawkins,nasko,mdempsky
BUG=456993
Original issue's description:
> Add namespace sandbox to about page.
>
> This unindents the lines about PID/network namespaces, since those now
> apply to both the setuid or unprivileged namespace sandbox.
>
> BUG=312380
> Committed: https://crrev.com/1ef7ee1ee899087d8632a4f905a3a11697a20b81
> Cr-Commit-Position: refs/heads/master@{#315116}

Committed: https://crrev.com/30c2c5d06c4cb04fda4985481155c5fc9c36d846
Cr-Commit-Position: refs/heads/master@{#315541}

[rickyz (no longer on Chrome), 2015-02-10 09:37:32]

rickyz@chromium.org changed reviewers:
+ hungte@chromium.org

[Hung-Te, 2015-02-10 09:38:12]

hungte@chromium.org changed reviewers:
+ magjed@chromium.org

[magjed_chromium, 2015-02-10 09:42:41]

The CQ bit was checked by magjed@chromium.org

[magjed_chromium, 2015-02-10 09:42:41]

lgtm

[commit-bot: I haz the power, 2015-02-10 09:43:07]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/872143006/1

[commit-bot: I haz the power, 2015-02-10 09:48:35]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-02-10 09:48:36]

Try jobs failed on following builders:
  chromium_presubmit on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/chromium_presub...)

[magjed_chromium, 2015-02-10 11:02:55]

The CQ bit was checked by magjed@chromium.org

[commit-bot: I haz the power, 2015-02-10 11:03:15]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/872143006/1

[commit-bot: I haz the power, 2015-02-10 11:58:47]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-10 11:59:32]

Patchset 1 (id:??) landed as
https://crrev.com/30c2c5d06c4cb04fda4985481155c5fc9c36d846
Cr-Commit-Position: refs/heads/master@{#315541}