chore: fix failing unit tests (GoogleCloudPlatform#244)

Author: Kenneth Rosario

tox.ini

@@ -4,7 +4,7 @@ envlist = py{35,36,37,38,39,310}-{ubuntu-latest,macos-latest,windows-latest},lin
 [testenv]
 usedevelop = true
 deps =
-    docker<5 # https://github.com/docker/docker-py/issues/2807
+    docker
     pytest-cov
     pytest-integration
     pretend