[R&D review] Harmonize virtual override keywords

[Quentin Garchery]

https://github.com/morpho-dao/morpho-tokenized-vaults/blob/6f182b04cf3326cf4244292f8533524236f0b773/src/compound/SupplyVaultBase.sol#L98

Should we also add the virtual keyword here, for harmonization ? All other overriden functions are kept virtual