Remove version env variable from firefox beta

Author: aguspe

rb/spec/tests.bzl

@@ -111,7 +111,6 @@ BROWSERS = {
         "env": {
             "WD_REMOTE_BROWSER": "firefox",
             "WD_SPEC_DRIVER": "firefox",
-            "WD_BROWSER_VERSION": "beta",
         } | select({
             "@selenium//common:use_pinned_linux_firefox": {
                 "FIREFOX_BINARY": "$(location @linux_beta_firefox//:firefox/firefox)",