Bug 1470100 - use a vector instead of an array for the list of prefs, r=ato

MozReview-Commit-ID: 5JI85Rif28M

--HG--
extra : rebase_source : ce4ee702166107d85b268f78d5efaa66eaa9ab2b

testing/geckodriver/src/prefs.rs

@@ -8,7 +8,7 @@ use mozprofile::preferences::Pref;
 // a Testing :: Marionette peer before you make any changes to this file.
 
 lazy_static! {
-    pub static ref DEFAULT: [(&'static str, Pref); 54] = [
+    pub static ref DEFAULT: Vec<(&'static str, Pref)> = vec![
         // Make sure Shield doesn't hit the network.
         ("app.normandy.api_url", Pref::new("")),