LibGfx: Don't expose anon_fd inside Gfx::ShareableBitmap

Nobody outside needs to see this, so let's just hide it.

Userland/Libraries/LibGfx/ShareableBitmap.cpp

@@ -47,7 +47,7 @@ bool encode(Encoder& encoder, const Gfx::ShareableBitmap& shareable_bitmap)
     encoder << shareable_bitmap.is_valid();
     if (!shareable_bitmap.is_valid())
         return true;
-    encoder << IPC::File(shareable_bitmap.anon_fd());
+    encoder << IPC::File(shareable_bitmap.bitmap()->anon_fd());
     encoder << shareable_bitmap.width();
     encoder << shareable_bitmap.height();
     return true;

Userland/Libraries/LibGfx/ShareableBitmap.h

@@ -39,8 +39,6 @@ public:
 
     bool is_valid() const { return m_bitmap; }
 
-    int anon_fd() const { return m_bitmap ? m_bitmap->anon_fd() : -1; }
-
     const Bitmap* bitmap() const { return m_bitmap; }
     Bitmap* bitmap() { return m_bitmap; }