Version-lock setup-chromedriver action

We're having troubles with this action failing on downloading the latest
Chromedriver.  It should apparently be fixed in the later master, but it
doesn't appear to work for us, so we'll lock to the latest commit for
now.

See nanasess/setup-chromedriver#200 for details.

.github/workflows/build-and-test.yml

@@ -68,7 +68,7 @@ jobs:
 
       - uses: browser-actions/setup-chrome@latest
       - run: chrome --version
-      - uses: nanasess/setup-chromedriver@master
+      - uses: nanasess/setup-chromedriver@a96f21134e877e799f5dce6cfb399e725bce27e2
 
       - name: "Set up PostgreSQL"
         uses: harmon758/postgresql-action@v1