minor #8034 Removing bower, as even they now recommend to use yarn and webpack (weaverryan)

This PR was squashed before being merged into the 2.7 branch (closes #8034).

Discussion
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Removing bower, as even they now recommend to use yarn and webpack

Check the note on: https://bower.io/

Let's remove this section entirely, and redirect to the frontend section in general.

Commits
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5a7610c fixing index problem now that there were *no* frontend articles on 2.7
4fe7bfb Removing bower, as even they now recommend to use yarn and webpack

Author: weaverryan

_build/redirection_map

@@ -162,7 +162,7 @@
 /cookbook/form/inherit_data_option /form/inherit_data_option
 /cookbook/form/unit_testing /form/unit_testing
 /cookbook/form/use_empty_data /form/use_empty_data
-/cookbook/frontend/bower /frontend/bower
+/cookbook/frontend/bower /frontend
 /cookbook/frontend/index /frontend
 /cookbook/install/unstable_versions /setup/unstable_versions
 /cookbook/install/bundles /setup/bundles

frontend.rst

@@ -1,8 +1,6 @@
 Front-end
 =========
 
-.. toctree::
-    :maxdepth: 1
-    :glob:
+See the latest version of the docs for frontend tools. Or, see
+:doc:`/assetic`.
 
-    frontend/*