Fix typos for custom requirements config options descriptions

This simply corrects some types for the custom requirements-related
config options' descriptions.

Change-Id: Ibcf4ef0895b365ad75a6714a9a9ec6445037422d
diff --git a/etc/patrole.conf.sample b/etc/patrole.conf.sample
index 5816ea9..518d38a 100644
--- a/etc/patrole.conf.sample
+++ b/etc/patrole.conf.sample
@@ -28,15 +28,15 @@
 
 #
 # This option determines whether Patrole should run against a
-# `custom_requirements_file` which defines RBAC requirements. The
+# ``custom_requirements_file`` which defines RBAC requirements. The
 # purpose of setting this flag to True is to verify that RBAC policy
 # is in accordance to requirements. The idea is that the
-# `custom_requirements_file` perfectly defines what the RBAC
+# ``custom_requirements_file`` perfectly defines what the RBAC
 # requirements are.
 #
 # Here are the possible outcomes when running the Patrole tests
 # against
-# a `custom_requirements_file`:
+# a ``custom_requirements_file``:
 #
 # YAML definition: allowed
 # test run: allowed
@@ -44,7 +44,7 @@
 #
 # YAML definition: allowed
 # test run: not allowed
-# test result: fail (under-permission)
+# test result: fail (under-permission, e.g. Forbidden exception)
 #
 # YAML definition: not allowed
 # test run: allowed
@@ -53,30 +53,32 @@
 #test_custom_requirements = false
 
 #
-# File path of the yaml file that defines your RBAC requirements. This
-# file must be located on the same host that Patrole runs on. The yaml
+# File path of the YAML file that defines your RBAC requirements. This
+# file must be located on the same host that Patrole runs on. The YAML
 # file should be written as follows:
 #
 # ```
-# <service>:
-#   <api_action>:
-#     - <allowed_role>
-#     - <allowed_role>
-#     - <allowed_role>
-#   <api_action>:
-#     - <allowed_role>
-#     - <allowed_role>
-# <service>
-#   <api_action>:
-#     - <allowed_role>
+# <service_foo>:
+#   <api_action_x>:
+#     - <allowed_role_a>
+#     - <allowed_role_b>
+#     - <allowed_role_c>
+#   <api_action_y>:
+#     - <allowed_role_d>
+#     - <allowed_role_e>
+# <service_bar>:
+#   <api_action_z>:
+#     - <allowed_role_b>
 # ```
+#
 # Where:
-# service = the service that is being tested (cinder, nova, etc)
+#
+# service = the service that is being tested (Cinder, Nova, etc.)
 # api_action = the policy action that is being tested. Examples:
 #              - volume:create
 #              - os_compute_api:servers:start
 #              - add_image
-# allowed_role = the Keystone role that is allowed to perform the API
+# allowed_role = the Keystone role that is allowed to perform the API.
 #  (string value)
 #custom_requirements_file = <None>