message: doc: remove redundant optionals from build-unix.md
  Calling dependencies optional in a list of already optional dependencies
  is redundant.
diff: @@ -43,12 +43,12 @@ Optional dependencies:
  ------------|------------------|----------------------
  miniupnpc | UPnP Support | Firewall-jumping support
  libnatpmp | NAT-PMP Support | Firewall-jumping support
  - libdb4.8 | Berkeley DB | Optional, wallet storage (only needed when legacy wallet enabled)
  + libdb4.8 | Berkeley DB | Wallet storage (only needed when legacy wallet enabled)
  qt | GUI | GUI toolkit (only needed when GUI enabled)
  - libqrencode | QR codes in GUI | Optional for generating QR codes (only needed when GUI enabled)
  - libzmq3 | ZMQ notification | Optional, allows generating ZMQ notifications (requires ZMQ version >= 4.0.0)
  - sqlite3 | SQLite DB | Optional, wallet storage (only needed when descriptor wallet enabled)
  - systemtap | Tracing (USDT) | Optional, statically defined tracepoints
  + libqrencode | QR codes in GUI | QR code generation (only needed when GUI enabled)
  + libzmq3 | ZMQ notification | ZMQ notifications (requires ZMQ version >= 4.0.0)
  + sqlite3 | SQLite DB | Wallet storage (only needed when descriptor wallet enabled)
  + systemtap | Tracing (USDT) | Statically defined tracepoints
  For the versions used, see [dependencies.md](dependencies.md)
  