[3.7] bpo-35054: Add more index entries for symbols. (GH-10064). (GH-10120)

(cherry picked from commit ddb961d2abe5d5fde76d85b21a77e4e91e0043ad)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
diff --git a/Doc/library/urllib.request.rst b/Doc/library/urllib.request.rst
index cbbec0c..982f57f 100644
--- a/Doc/library/urllib.request.rst
+++ b/Doc/library/urllib.request.rst
@@ -297,7 +297,7 @@
    Cause requests to go through a proxy. If *proxies* is given, it must be a
    dictionary mapping protocol names to URLs of proxies. The default is to read
    the list of proxies from the environment variables
-   :envvar:`<protocol>_proxy`.  If no proxy environment variables are set, then
+   ``<protocol>_proxy``.  If no proxy environment variables are set, then
    in a Windows environment proxy settings are obtained from the registry's
    Internet Settings section, and in a Mac OS X environment proxy information
    is retrieved from the OS X System Configuration Framework.