[dv/clkmgr] Fix doc punctuation

Fix a punctuation issue raised on a prior PR.

Signed-off-by: Guillermo Maturana <maturana@google.com>
diff --git a/hw/ip/clkmgr/data/clkmgr_testplan.hjson b/hw/ip/clkmgr/data/clkmgr_testplan.hjson
index 9dff37c..13ce1b1 100644
--- a/hw/ip/clkmgr/data/clkmgr_testplan.hjson
+++ b/hw/ip/clkmgr/data/clkmgr_testplan.hjson
@@ -107,7 +107,7 @@
             - Setting `scanmode_i`.
 
             **Checks**:
-            Clock divider checks: since `scanmode_i` is asynchronous the checks
+            Clock divider checks: since `scanmode_i` is asynchronous, the checks
             are performed in behavioral code in the scoreboard; SVA assertions
             will be added, conditioned on scanmode being off.
             - When the external clock is selected (and not defeated by