www/grafana9: enable on riscv64

Builds fine on riscv64, but build fails on armv7:

> Generating wire_gen.go

runtime: out of memory: cannot allocate 4194304-byte block (1945894912 in use)
fatal error: out of memory

Sponsored by: Berliner Linux User Group e.V.
Approved by: portmgr (build fix blanket)