Use .tar.gz for test archives

Differential Revision: https://phabricator.services.mozilla.com/D1743

bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=733530
gecko-commit: 6f2020891542fbc0010d555812a289038095a4ef
gecko-integration-branch: autoland
gecko-reviewers: gps

README.md

@@ -133,11 +133,11 @@ And on macOS with homebrew using:
 brew install nss
 ```
 
-On other platforms, download the firefox archive and common.tests.zip
+On other platforms, download the firefox archive and common.tests.tar.gz
 archive for your platform from
 [Mozilla CI](https://archive.mozilla.org/pub/firefox/nightly/latest-mozilla-central/).
 
-Then extract `certutil[.exe]` from the tests.zip package and
+Then extract `certutil[.exe]` from the tests.tar.gz package and
 `libnss3[.so|.dll|.dynlib]` and put the former on your path and the latter on
 your library path.