Deploy swh-graph v6.1.0

(No hurry, I'm just opening an issue to track this)

There is one breaking change that affects you: the command to install the gRPC server changed:

• cargo install --features=grpc-server swh-graph -> cargo install swh-graph-grpc-server
• cargo install --git https://gitlab.softwareheritage.org/swh/devel/swh-graph.git --features grpc-server swh-graph -> cargo install --git https://gitlab.softwareheritage.org/swh/devel/swh-graph.git swh-graph-grpc-server
• (from the git repo) cargo build --release --features grpc-server -p swh-graph -> cargo build --release -p swh-graph-grpc-server

and if you ran the gRPC server with the -vv option (to get INFO log level), you need to remove it, it's now INFO by default, and -vvv was replaced with the RUST_LOG=debug env var.

Plan:

• granet: Upgrade graph version in venv
• Upgrade graph go binaries (one of the command above ^)
• Restart systemd service swh-graph-grpc & swh-graph-http
• Tag grafana
• Checks
• swh/devel/swh-docs!447 (merged): graph: Update documentation about manual upgrade (in granet)