BG3515 Increase P2SH input size estimate to 296
BG3515 Increase P2SH input size estimate to 296

Summary: We have noticed that our transaction size sometimes underestimates slightly and are increasing the P2SH input size estimate by one byte to mitigate this

Reviewers: kevin

Reviewed By: kevin

Differential Revision: https://phabricator.bitgo.com/D7882

BitGo/bitgo-cli