Update ddtrace to ^0.55.4 (#192)

Updating to latest version of ddtrace. Update process: 1. Update `ddtrace` version in `pyproject.toml` 2. Run `poetry update ddtrace`

Author: brettlangdon

poetry.lock

@@ -26,7 +26,7 @@ classifiers = [
 python = ">=3.6.0,<4"
 datadog = "^0.41.0"
 wrapt = "^1.11.2"
-ddtrace = "^0.50.0"
+ddtrace = "^0.55.4"
 importlib_metadata = {version = "^1.0", python = "<3.8"}
 boto3 = { version = "^1.10.33", optional = true }
 requests = { version ="^2.22.0", optional = true }