Gello: Make incognito sentence fully translatable

Stray '.' didn't fall under translation scope

Change-Id: I7fa1801d85bbf276beb9488633fcc4fc21fdf662
diff --git a/res/raw/incognito_mode_start_page.html b/res/raw/incognito_mode_start_page.html
index 7208e4b..1fac650 100644
--- a/res/raw/incognito_mode_start_page.html
+++ b/res/raw/incognito_mode_start_page.html
@@ -38,7 +38,7 @@
   <body>
     <p>
     <p>
-    <strong>You've gone incognito</strong>.
+    <strong>You've gone incognito.</strong>
     <p> Pages you view in this window won't appear in your browser history or
       search history, and they won't leave other traces, like cookies, on your
       device after you close the incognito window. Any files you download or