Update MANUAL_INSTRUCTIONS.md

use cut to stripg the 0x prefix

Author: strk

MANUAL_INSTRUCTIONS.md

@@ -24,7 +24,7 @@ The following can be done in a Docker container for additional isolation, includ
 12. `openssl ec -inform der -in eth_key.der > eth.key`
 13. Prepare a message to sign:
     - Take your ethereum address _without_ the '0x' prefix.
-    - `UNSIGNED_MSG="$(echo -n $'\x19Ethereum Signed Message:\n'20 | xxd -p)<your ethereum address without 0x>"`
+    - `UNSIGNED_MSG="$(echo -n $'\x19Ethereum Signed Message:\n'20 | xxd -p)$(echo $ETH_ADDR | cut -c3-)"`
     - `echo -n "$UNSIGNED_MSG" | xxd -r -p | ~/.cargo/bin/sha3sum -a Keccak256` to get your signed message hash. The first part of this output is your hash, set it as `$HASH`. The short-form of this is (the nbsp separator makes this look odd): `HASH=$(echo -n "$UNSIGNED_MSG" | xxd -r -p | ~/.cargo/bin/sha3sum -a Keccak256 | awk -F $'\xC2\xA0' '{ print $1 }')`
 14. With HASH as the hex output of the signed message hash above, `SIGNATURE_HEX=$(echo $HASH | xxd -r -p | openssl pkeyutl -sign -inkey eth.key | xxd -p -c 72)`
 15. You now have all elements of your proof, make a CSV form of them: `echo "${USER_ID},${ETH_ADDR},${SIGNATURE_HEX},${MERKLE_PROOF}"`