Trivial: Fix some document comments in microversion

This is follow up patch to fix doc comments left in
Icbdcfb4cd5b7fb1029eec035b9e0024be59c8d1f

Change-Id: Iebdbfd62d1db4088e7e356aae700b74c17888415
diff --git a/doc/source/library/api_microversion_testing.rst b/doc/source/library/api_microversion_testing.rst
index 0d0b595..b7a4ba8 100644
--- a/doc/source/library/api_microversion_testing.rst
+++ b/doc/source/library/api_microversion_testing.rst
@@ -8,7 +8,7 @@
 ---------------------------------------------
 
 Many of the OpenStack components have implemented API microversions.
-It is important to tests those microversion in Tempest or external plugins.
+It is important to test those microversions in Tempest or external plugins.
 Tempest now provides stable interfaces to support to test the API microversions.
 Based on the microversion range coming from the combination of both configuration
 and each test case, APIs request will be made with selected microversion.