Fix typo in tempest configuration guide
The indefinite article of the word "alternate" had became "a".
Fix it to "an".
Closes-Bug #1486786
Change-Id: I8d66d066f218fdb3cb70e45ebbcc6be6ae2e5925
diff --git a/doc/source/configuration.rst b/doc/source/configuration.rst
index 3e6013d..9d1a143 100644
--- a/doc/source/configuration.rst
+++ b/doc/source/configuration.rst
@@ -24,7 +24,7 @@
Tempest currently has 2 different ways in configuration to provide credentials
to use when running tempest. One is a traditional set of configuration options
in the tempest.conf file. These options are in the identity section and let you
-specify a regular user, a global admin user, and a alternate user set of
+specify a regular user, a global admin user, and an alternate user set of
credentials. (which consist of a username, password, and project/tenant name)
These options should be clearly labelled in the sample config file in the
identity section.