Change install-spike.sh to get the sources from cvv

[MarioOpenHWGroup]

Main changes to cva6 repo:

• Change target on install-spike
• Delete vendor/riscv/riscv-isa-sim

[zarubaf]

Looks like a good change!

[github-actions]

✔️ successful run, report available here.

[cathales]

Missing removals (see openhwgroup/core-v-verif#2250):

• vendor/patches/riscv/riscv-isa-sim/ (done in Delete vendor/patches/riscv/riscv-isa-sim directory #1545)
• vendor/riscv_riscv-isa-sim.lock.hjson
• vendor/riscv_riscv-isa-sim.vendor.hjson