Merge pull request #345 from percona/copilot/sub-pr-342

Clarify `{USER}` placeholder in Kerberos manual ticket authentication section

Author: rasika-chivate

docs/details/authentication.md

@@ -154,8 +154,10 @@ You can choose any of these methods to authenticate `pbm` user against Kerberos:
          sudo -u {USER} kinit <username>@<KERBEROS_REALM>
          ```
      
+         where `{USER}` is the OS user account that runs the `pbm-agent` process.
+     
          !!! note 
-            Run the `pbm-agent` process as **{USER}**. PBM does not refresh its authentication ticket automatically, so when the ticket expires you must obtain a new one.
+            Run the `pbm-agent` process as `{USER}`. PBM does not refresh its authentication ticket automatically, so when the ticket expires you must obtain a new one.
      
      2. Specify the following MongoDB connection URI without the password.