cargo: use rocket_prometheus 0.10.0-rc.1

Fixes #167

Cargo.lock

@@ -2505,8 +2505,9 @@ dependencies = [
 
 [[package]]
 name = "rocket_prometheus"
-version = "0.9.0"
-source = "git+https://github.com/sd2k/rocket_prometheus?branch=async#a913a451555ba1344e88c9e730c4164b20032c40"
+version = "0.10.0-rc.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "738c535f2b35b4040c7cc9dfc6f3f32e4062809ce84387e50fe0b604b4d2d91f"
 dependencies = [
  "prometheus",
  "rocket",

Cargo.toml

@@ -33,7 +33,7 @@ num_cpus = "1.0"
 ring = "0.13"
 base64 = "0.10"
 uuid = { version = "0.7", features = [ "v4" ] }
-rocket_prometheus = { git = "https://github.com/sd2k/rocket_prometheus", branch = "async" }
+rocket_prometheus = "0.10.0-rc.1"
 lazy_static = "1.3.0"
 gettext-macros = "0.6"
 gettext-utils = "0.1"