Bug 1590935 - Offer to re-enable TLS 1.0 on SSL_ERROR_PROTOCOL_VERSION_ALERT, r=johannh

As it turns out, there are some sites that generate this error.  It's a small
number, but enough to justify the change.

No new tests because we can't generate this condition in our test setup.

Differential Revision: https://phabricator.services.mozilla.com/D50396

--HG--
extra : moz-landing-system : lando

browser/base/content/aboutNetError.js

@@ -277,7 +277,9 @@ function initPage() {
     setupErrorUI();
 
     const errorCode = document.getNetErrorInfo().errorCodeString;
-    const isTlsVersionError = errorCode == "SSL_ERROR_UNSUPPORTED_VERSION";
+    const isTlsVersionError =
+      errorCode == "SSL_ERROR_UNSUPPORTED_VERSION" ||
+      errorCode == "SSL_ERROR_PROTOCOL_VERSION_ALERT";
     const tls10OverrideEnabled = RPMGetBoolPref(
       "security.tls.version.enable-deprecated"
     );