docs: Exclude files from TOC warnings and navigation sidebar.

Sphinx was displaying "WARNING: document isn't included in any toctree"
for files we just don't want in the TOC. We can hide them from the index,
but the rtd theme defaults to display hidden index entries in the nav bar.

This commit excludes these files from such warnings, and patches layout.html
so that hidden index entries stay hidden from the navigation sidebar.

This commit also moves password-strength.md under docs/production and
adds it as a hidden entry in production/index.rst.

Fixes #7417.

docs/_templates/layout.html

@@ -131,7 +131,7 @@
               toctree is empty. Skip building this for now.
             #}
             {% if 'singlehtml' not in builder %}
-              {% set global_toc = toctree(maxdepth=theme_navigation_depth|int, collapse=theme_collapse_navigation, includehidden=True) %}
+              {% set global_toc = toctree(maxdepth=theme_navigation_depth|int, collapse=theme_collapse_navigation, includehidden=False) %}
             {% endif %}
             {% if global_toc %}
               {{ global_toc }}

docs/development/index.rst

@@ -10,3 +10,8 @@ Development Environment
    Advanced Setup (non-Vagrant) <setup-advanced>
    Using the development environment <using>
    Developing remotely <remote>
+
+.. toctree::
+   :hidden:
+
+   request-remote

docs/production/index.rst

@@ -17,3 +17,11 @@ Zulip in Production
    postgres
    ssl-certificates
    email
+
+.. toctree::
+   :hidden:
+
+   expensive-migrations
+   install-existing-server
+   multiple-organizations
+   password-strength

docs/production/security-model.md

@@ -64,7 +64,7 @@ strength allowed is controlled by two settings in
   significant protection against online attacks, while limiting the
   burden imposed on users choosing a password.
 
-  <!--- Why 10000?  See password-strength.md. -->
+  <!--- Why 10000?  See /production/password-strength.md. -->
 
   Estimating the guessability of a password is a complex problem and
   impossible to efficiently do perfectly. For background or when