fix(test): use routerOptions.constraints to avoid FSTDEP022 warning

[Tony133]

Proposal:

Fixes the FSTDEP022 deprecation warning shown when running the test suite on Fastify v5 ( see screenshot )

The constraints and constraints with unconstrained routes tests create the Fastify instance with constraints as a top-level option, which is deprecated in v5 and will be removed in v6:

// before
const server = Fastify({
  constraints: { testConstraint: getTestConstraint() }
})

// after
const server = Fastify({
  routerOptions: {
    constraints: { testConstraint: getTestConstraint() }
  }
})

Only test/test.js is affected — index.js uses constraints at the route level (fastify.route()), which is a different, non-deprecated option.

Note:

• Verified: node --test test/test.js test/websocket.js → all passing, no warnings, coverage unchanged.