[UI]update rocket icon to emoji #18729

Description:

Fixes: #18700
update rocket icon to emoji.
It seems like the emoji Character does not exist in the Travis, Exist in GitHub action. see here

Review

• [ ] Functional review done
• [ ] Potential edge cases thought about (behavior of the code with strange input, with strange internal state or possible interactions with other Matomo subsystems)
• [ ] Usability review done (is anything maybe unclear or think about anything that would cause people to reach out to support)
• [ ] Security review done
• [ ] Wording review done
• [ ] Code review done
• [ ] Tests were added if useful/possible
• [ ] Reviewed for breaking changes
• [ ] Developer changelog updated if needed
• [ ] Documentation added if needed
• [ ] Existing documentation updated if needed

If the font icon isn't in use anymore, I guess we can also remove it again

@sgiehl it seems like there are lots of places using Rocket Icon. Do we want to replace all of them with emojis? Otherwise, I think removing the icon will break some parts, some js Tests has click event on .icon-rocket

@tsteur Shall we replace all usages of the rocket icon with the emoji, or only that specific one?

not needed for now @sgiehl