minor symfony#4196 Clarified the bundle base template bit. (Veltar)

This PR was submitted for the 2.5 branch but it was merged into the 2.3 branch instead (closes symfony#4196).

Discussion
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Clarified the bundle base template bit.

Commits
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eae1a03 Clarified the bundle base template bit.

Author: weaverryan

book/templating.rst

@@ -413,6 +413,8 @@ lives in a specific location:
   that's specific to the ``AcmeBlogBundle``. Since the middle, "controller",
   portion is missing (e.g. ``Blog``), the template lives at
   ``Resources/views/layout.html.twig`` inside ``AcmeBlogBundle``.
+  Note that the colon is not removed with the "controller", and two colons exist
+  between the "bundle"name and template file name.
 
 * ``::base.html.twig``: This syntax refers to an application-wide base template
   or layout. Notice that the string begins with two colons (``::``), meaning