build-unit-test-docker: use latest gitlint

gitlint release 0.18.0 contains the previously pointed to commit,
so pull it in directly rather than by reference now.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I741b0bbfe88f5361a4324bafdf7af883ad1a51c1
diff --git a/scripts/build-unit-test-docker b/scripts/build-unit-test-docker
index 76f19d1..d0b48d3 100755
--- a/scripts/build-unit-test-docker
+++ b/scripts/build-unit-test-docker
@@ -834,14 +834,7 @@
 RUN pip3 install protobuf
 RUN pip3 install codespell
 RUN pip3 install requests
-"""
-
-# Note, we use sha1s here because the newest gitlint release doesn't include
-# some features we need.  Next time they release, we can rely on a direct
-# release tag
-dockerfile_base += """
-RUN pip3 install git+https://github.com/jorisroovers/gitlint.git@8ede310d62d5794efa7518b235f899f8a8ad6a68\\#subdirectory=gitlint-core
-RUN pip3 install git+https://github.com/jorisroovers/gitlint.git@8ede310d62d5794efa7518b235f899f8a8ad6a68
+RUN pip3 install gitlint
 """
 
 # Build the base and stage docker images.