fix doc gate

Fix documentation build by correcting a source filename and fixing
the dependency settings.

Change-Id: I1fc098cef7097ffea338129a3fcefda77f396a3a
Signed-off-by: Doug Hellmann <doug@doughellmann.com>

doc/source/install/index.rst

@@ -1,8 +1,7 @@
-====================================
-  oslo.limit Installation Tutorial
-====================================
+==============
+ Installation
+==============
 
-.. toctree::
-   :maxdepth: 1
+At the command line::
 
-   installation
+    $ pip install oslo.limit

doc/source/install/installation.rst

@@ -1,7 +0,0 @@
-==============
- Installation
-==============
-
-At the command line::
-
-    $ pip install oslo.limit

tox.ini

@@ -26,9 +26,11 @@ basepython = python3
 commands = {posargs}
 
 [testenv:docs]
-basepython = python3
 deps =
+  -r{toxinidir}/test-requirements.txt
+  -r{toxinidir}/requirements.txt
   -r{toxinidir}/doc/requirements.txt
+basepython = python3
 commands = sphinx-build -W -b html doc/source doc/build/html
 
 [testenv:cover]