Bug 1450973 - Update the containers about page text to use a camel case title. r=jkt

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

@@ -861,7 +861,7 @@ userContextBanking.accesskey = B
 userContextShopping.accesskey = S
 userContextNone.accesskey = N
 
-userContext.aboutPage.label = Manage containers
+userContext.aboutPage.label = Manage Containers
 userContext.aboutPage.accesskey = O
 
 userContextOpenLink.label = Open Link in New %S Tab