Remove Brave's implementation of navigator.plugins farbling

Due to the removal of flash, navigator.plugins will always report an
empty array from now on, so there's no need for Brave to implement a
farbling mechanism for such array any more.

Thus, we can now remove all the code added to implement that and drop
a couple of patches to upstream's Chromium in the way too.

Main related issues in Brave's GitHub:

  * Fingerprinting 2.0: Plugins
    brave/brave-browser#9435

  * Fingerprinting 2.0: Plugins (word replacement)
    brave/brave-browser#10597

Chromium change:

https://chromium.googlesource.com/chromium/src.git/+/f8fe422e0e8a026f73f9d74d26f75c3c93102030

commit f8fe422e0e8a026f73f9d74d26f75c3c93102030
Author: Mason Freed <masonfreed@chromium.org>
Date:   Wed Jan 20 18:50:56 2021 +0000

    Empty out navigator.plugins and navigator.mimeTypes

    With this CL, navigator.plugins and navigator.mimeTypes will
    both return empty arrays.

    With the removal of Flash, there is no longer the need to
    return anything for navigator.plugins and navigator.mimeTypes.
    These APIs were used primarily for a) probing for Flash player
    support, or b) fingerprinting. As such, we'd like to return
    empty for these two properties. Gecko already switched to
    returning *only* Flash starting with Firefox 52, and returning
    empty as of Firefox 85.

    I2S:
    https://groups.google.com/a/chromium.org/g/blink-dev/c/bbxAGu90LgM

    Fixed: 1164635

browser/farbling/BUILD.gn

@@ -32,7 +32,6 @@ if (!is_android) {
       "brave_enumeratedevices_farbling_browsertest.cc",
       "brave_navigator_devicememory_farbling_browsertest.cc",
       "brave_navigator_hardwareconcurrency_farbling_browsertest.cc",
-      "brave_navigator_plugins_farbling_browsertest.cc",
       "brave_navigator_useragent_farbling_browsertest.cc",
       "brave_offscreencanvas_farbling_browsertest.cc",
       "brave_webaudio_farbling_browsertest.cc",