Correct Wikidata icon color in overflow menu

This icon's stroke was explicitly set to `#000` before this commit, but
we need its color to be `#54595d` to match the other icons in the
overflow menu [1]. Unfortunately, although we set a variant in skin.json
for the icon to be colored this way [2], there are 2 problems that
prevent it from displaying this color:

1) The icon sets an explicit black color for its stroke attribute
2) ResourceLoader currently only sets the fill color on the `g` element
when applying the variant style [3]. It does not set the stroke color. Even
if problem 1) was removed, we would need RL to set the stroke color, but
I'm not sure how that would affect other variant icons that RL deals
with.

The simplest possible solution is to to change the stroke attribute on
the icon itself, although it unfortunately introduces technical debt as
this icon now differs slightly from the OOUI one :(

[1] https://phabricator.wikimedia.org/T222630#5266575
[2] https://github.com/wikimedia/mediawiki-skins-MinervaNeue/blob/master/skin.json#L262-L267
[3] 4e59467427/includes/resourceloader/ResourceLoaderImage.php (L331)

Bug: T222630
Change-Id: I8c10a6012c7d32ab8555b874e766bc2f36437cf8

resources/wikimedia.ui/logo-Wikidata.svg

@@ -1 +1 @@
-<?xml version="1.0" encoding="UTF-8"?><svg xmlns="http://www.w3.org/2000/svg" width="20" height="20" stroke-width="30.2" viewBox="0 0 20 20"><title>Wikidata logo</title><path stroke="#000" stroke-width=".743" d="M.371 4v12.257m1.482 0V4m.74 0v12.257m.741 0V4m1.481 0v12.257m.741 0V4m.74 0v12.257M7.778 4v12.257m1.481 0V4m8.888 0v12.257m1.482 0V4M10.74 4v12.257m.741 0V4m.741 0v12.257m1.481 0V4m1.482 0v12.257m.74 0V4m.74 0v12.257"/></svg>
+<?xml version="1.0" encoding="UTF-8"?><svg xmlns="http://www.w3.org/2000/svg" width="20" height="20" stroke-width="30.2" viewBox="0 0 20 20"><title>Wikidata logo</title><path stroke="#54595d" stroke-width=".743" d="M.371 4v12.257m1.482 0V4m.74 0v12.257m.741 0V4m1.481 0v12.257m.741 0V4m.74 0v12.257M7.778 4v12.257m1.481 0V4m8.888 0v12.257m1.482 0V4M10.74 4v12.257m.741 0V4m.741 0v12.257m1.481 0V4m1.482 0v12.257m.74 0V4m.74 0v12.257"/></svg>