last 1000 RAO of a wallet cannot be staked / delegated (should be 500)

[pawelpolewicz]

Describe the bug

bittensor/bittensor/extrinsics/delegation.py:delegate_extrinsic()
and bittensor/bittensor/extrinsics/staking.py:add_stake_extrinsic()
do not use bittensor/subtensor.py:get_existential_deposit (which on mainnet returns 500 RAO) and use a hardcoded 1000 RAO instead.

To Reproduce

try to stake or delegate everything

Expected behavior

only existentialDeposit should remain in the wallet

Screenshots

No response

Environment

any

Additional context

No response