Disable Wallet button on Tor/Private windows

[srirambv]

Description

Following up on #18455, we should disable the wallet buttons on private and Tor windows similar to rewards button. we can revert this change once window.ethereum is enabled on Tor/Private windows

cc: @jamesmudgett @bbondy

[stephendonner]

Verified PASSED using

Brave	1.32.94 Chromium: 95.0.4638.69 (Official Build) beta (64-bit)
Revision	6a1600ed572fedecd573b6c2b90a22fe6392a410-refs/branch-heads/4638@{#984}
OS	Windows 10 Version 20H2 (Build 19042.1288)

Confirmed there are no wallet icons on Guest, Private, and Private with Tor windows.

Guest	Private	Private with Tor

---

Verified PASSED using

Brave	1.32.103 Chromium: 96.0.4664.45 (Official Build) (x86_64)
Revision	76e4c1bb2ab4671b8beba3444e61c0f17584b2fc-refs/branch-heads/4664@{#947}
OS	macOS Version 11.6.1 (Build 20G224)

Confirmed there are no wallet icons on Guest, Private, and Private with Tor windows.

Guest	Private	Private with Tor

---

Verified PASSED using

Brave	1.32.103 Chromium: 96.0.4664.45 (Official Build) (64-bit)
Revision	76e4c1bb2ab4671b8beba3444e61c0f17584b2fc-refs/branch-heads/4664@{#947}
OS	Linux

Confirmed there are no wallet icons on Guest, Private, and Private with Tor windows.

Guest	Private	Private with Tor