[doc] Fix qemu-riscv64 command line flag (#34866)
### Details:
- riscv-collab toolchain uses updated flag for enabling vector extension
(RVV) usage on qemu-riscv64 emulator
### Tickets:
- N/A
### AI Assistance:
- *AI assistance used: no*
Co-authored-by: Nesterov Alexander <alexander.nesterov@intel.com>
