Update test/setup_travis.sh (#19878)

* Update test/setup_travis.sh

* Obtain the latest geckodriver version using a bash trick

This trick comes from the repository of privacybadger

EFForg/privacybadger@1550b9e

Author: cschanaj

test/setup_travis.sh

@@ -17,9 +17,9 @@ function setup_chrome {
 }
 
 function setup_firefox {
-    # install the latest version of geckodriver (per Github release API)
+    # install the latest version of geckodriver
     firefox_version=$("${BROWSER}" -version)
-    geckodriver_version=$(curl -s https://api.github.com/repos/mozilla/geckodriver/releases/latest | grep tag_name | cut -d '"' -f 4)
+    geckodriver_version=$(curl -sI https://github.com/mozilla/geckodriver/releases/latest | grep -i "^Location: " | sed 's/.*\///' | tr -d '\r')
     geckodriver_url="https://github.com/mozilla/geckodriver/releases/download/${geckodriver_version}/geckodriver-${geckodriver_version}-linux64.tar.gz"
 
     echo "Setting up geckodriver ${geckodriver_version} for ${firefox_version}"