[NPU] Update README for 5020 (#35041)
### Details:
- Update README for 5020
### Tickets:
- [CVS-181693](https://jira.devtools.intel.com/browse/CVS-181693)
### AI Assistance:
- *AI assistance used: no / yes*
- *If yes, summarize how AI was used and what human validation was
performed (build/tests/manual checks).*
Signed-off-by: Sorin Butnariu <sorin.butnariu@intel.com>
