os2: remove return on file_size error from read_entire_file

file_size can't return .No_Size because it uses io.size and only returns
an io.Error, removing this so it works when file_size fails (linux pipes
for instance)

core/os/os2/file_util.odin

@@ -125,9 +125,6 @@ read_entire_file_from_file :: proc(f: ^File, allocator: runtime.Allocator) -> (d
 			has_size = true
 			size = int(size64)
 		}
-	} else if serr != .No_Size {
-		err = serr
-		return
 	}
 
 	if has_size && size > 0 {