Remove unused social icon files and project references (#10730)

related
#10723
#10707

Author: SimonCropp

src/NuGetGallery/Content/gallery/img/facebook-24x24.png

@@ -1374,8 +1374,6 @@
     <Content Include="Areas\Admin\DynamicData\PageTemplates\ListDetails.aspx" />
     <Content Include="Content\admin\SupportRequestStyles.css" />
     <Content Include="Content\fabric.css" />
-    <Content Include="Content\gallery\img\facebook.svg" />
-    <Content Include="Content\gallery\img\facebook-24x24.png" />
     <Content Include="Content\gallery\img\logo-og-600x600.png" />
     <Content Include="Content\gallery\img\rss-24x24.png" />
     <Content Include="Content\gallery\img\trusted-publisher-256x256.png" />
@@ -1384,8 +1382,6 @@
     <Content Include="Content\gallery\img\trusted-publisher-disabled.svg" />
     <Content Include="Content\gallery\img\trusted-publisher-temporary-256x256.png" />
     <Content Include="Content\gallery\img\trusted-publisher-temporary.svg" />
-    <Content Include="Content\gallery\img\x.svg" />
-    <Content Include="Content\gallery\img\x-24x24.png" />
     <Content Include="Content\Images\icons\apiKey.png" />
     <Content Include="Content\Images\icons\apiKeyExpired.png" />
     <Content Include="Content\Images\icons\apiKeyLegacy.png" />