For starters, you can directly upload the file on-site. No need to use some sketchy hosting site.
Next, the file you uploaded has nothing but garbled nonsense.
For a file to be truly be a save, it needs to have gaps in data so that partitions can be recognizable.
So this file may be named "sav", but it is completely not a save.
If I understand this right, you tried using the GBA Backup Tool with your LeafGreen cart? It's possible that your cart is fake. The backup tool only works with real carts (this is due to how real vs fake store the save in their hardware)
TL;DR: Your backup method is probably wrong, or your cart is fake. Either way this file isn't a save. PKHeX can't read it, simply because it isn't one.