[Cashtab] Refactor token icon link

Summary: Removed /32/ from tokenIconUrl baselink and inserted /32/ in areas of the code referencing tokenIconUrl. Related to task T2014

Test Plan:
cd web/cashtab && npm start
ensure token icons are displaying correctly in the Tx component
navigate to eTokens Page
ensure each token list item's icon is displaying correctly in the TokenList component

Reviewers: bytesofman, #bitcoin_abc

Reviewed By: bytesofman, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D10593