message: docs: fix broken link
  fault_injection -> fault-injection
diff: @@ -152,7 +152,7 @@ features. The following sandboxes are available:
  sandboxes/jaeger_native_tracing
  sandboxes/grpc_bridge
  Lua <https://github.com/envoyproxy/envoy/tree/master/examples/lua>
  - Fault Injection <https://github.com/envoyproxy/envoy/tree/master/examples/fault_injection>
  + Fault Injection <https://github.com/envoyproxy/envoy/tree/master/examples/fault-injection>
  Other use cases
  ---------------
  