Deltafi Token Logo Update

[leqiang-deltafi]

• I'm submitting a ...
  [ ] bug report
  [ *] feature request
  [ ] question about the decisions made in the repository
  [ ] question about how to use this project

• Summary
  Just update the logo of deltafi token, the only change is logo image in the asset folder

• Other information (e.g. detailed explanation, stack traces, related issues, suggestions how to fix, links for us to have context, eg. StackOverflow, personal fork, etc.)
  PR for updating the logo: Deltafi Token Logo Update #30027
  PR for adding the token: deltafi-token #19479