chore: bizhawk app icon, minui initials

BizHawk's tile takes EmuHawk's application icon (ApplicationIcon in its csproj) instead of an account avatar. MinUI has no logo of its own: its entry and copy go, and fetch_site_images.py now removes the copy of a platform without a logo.

docs_assets/logos/sources.json

@@ -18,7 +18,7 @@
     {
       "file": "bizhawk.webp",
       "platform": "bizhawk",
-      "source": "https://avatars.githubusercontent.com/u/11743303",
+      "source": "https://raw.githubusercontent.com/TASEmulators/BizHawk/master/src/BizHawk.Client.EmuHawk/images/logo.ico",
       "owner": "TASVideos",
       "licence": "GitHub organisation avatar of TASEmulators"
     },
@@ -50,13 +50,6 @@
       "owner": "Lakka (libretro)",
       "licence": "file from libretro/retroarch-assets, CC-BY-4.0"
     },
-    {
-      "file": "minui.webp",
-      "platform": "minui",
-      "source": "https://avatars.githubusercontent.com/u/225589",
-      "owner": "Shaun Inman",
-      "licence": "GitHub avatar of shauninman, the author of MinUI"
-    },
     {
       "file": "misterfpga.webp",
       "platform": "misterfpga",