Remove "data" checks from FILESYSTEM_mountassets()

After reasoning about it for a bit, there's no reason for these checks
to be here. `zip_normal` will either be
/home/infoteddy/.local/share/VVVVVV/levels if the asset directory is a
directory, or levels/levelname.zip if the asset directory is inside the
same zip as the level is. I don't see how they could ever be data.zip.

My guess is because of the VCE bug where it messed up its search path,
and before that bug was fixed, it had to be worked around here by
explicitly blacklisting data.zip here. When the assets mounting stuff
was ported from VCE to vanilla, vanilla didn't have the problem, and so
this data.zip blacklisting stuff was unnecessary.

Either way, I see no reason for this, so I'm going to remove it.

desktop_version/src/FileSystemUtils.cpp

@@ -240,10 +240,7 @@ void FILESYSTEM_mountassets(const char* path)
 
 		FILESYSTEM_assetsmounted = true;
 	}
-	else if (zip_normal != NULL
-	&& SDL_strcmp(zip_normal, "data.zip") != 0
-	&& !endsWith(zip_normal, "/data.zip")
-	&& endsWith(zip_normal, ".zip"))
+	else if (zip_normal != NULL && endsWith(zip_normal, ".zip"))
 	{
 		PHYSFS_File* zip = PHYSFS_openRead(zip_normal);