remove unused code/deps

Cargo.lock

@@ -1049,15 +1049,6 @@ dependencies = [
  "system-deps",
 ]
 
-[[package]]
-name = "generational-arena"
-version = "0.2.9"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "877e94aff08e743b651baaea359664321055749b398adff8740a7399af7796e7"
-dependencies = [
- "cfg-if",
-]
-
 [[package]]
 name = "generic-array"
 version = "0.14.7"
@@ -1960,7 +1951,6 @@ dependencies = [
  "capnpc",
  "clap",
  "futures",
- "generational-arena",
  "http",
  "oo7",
  "rand",