Bug 1567784 - Part 1: Add a string for the tooltip of the 'not secure' lock icon. r=johannh,flod

Differential Revision: https://phabricator.services.mozilla.com/D41075

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

browser/locales/en-US/chrome/browser/browser.properties

@@ -485,6 +485,7 @@ identity.ev.contentOwner=Site owned by: %S
 # Keep this string as short as possible, this is displayed in the URL bar
 # use a synonym for "safe" or "private" if "secure" is too long.
 identity.notSecure.label=Not Secure
+identity.notSecure.tooltip=Connection is not secure
 
 identity.extension.label=Extension (%S)
 identity.extension.tooltip=Loaded by extension: %S