chore: strip dotenv (unmaintained) from project

It is no longer needed as configuration is loaded via. TOML or direct env if appropriate.

Cargo.lock

@@ -2004,12 +2004,6 @@ version = "0.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0688c2a7f92e427f44895cd63841bff7b29f8d7a1648b9e7e07a4a365b2e1257"
 
-[[package]]
-name = "dotenv"
-version = "0.15.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "77c90badedccf4105eca100756a0b1289e191f6fcbdadd3cee1d2f614f97da8f"
-
 [[package]]
 name = "dtoa"
 version = "1.0.9"
@@ -5652,7 +5646,6 @@ dependencies = [
  "async-std",
  "cached",
  "config",
- "dotenv",
  "futures-locks",
  "log",
  "once_cell",
@@ -5720,7 +5713,6 @@ dependencies = [
  "bitfield",
  "chrono",
  "dashmap",
- "dotenv",
  "env_logger",
  "futures",
  "impl_ops",