Fix formating in ostree guide

Fix some formating issues, remarks and command names.

content/guides/ostree.md

@@ -76,7 +76,7 @@ situation for incorrect upgrade and revert the system to the previous
 state. More details are available in [manual test of
 rollback](https://qa.apertis.org/apertis-update-manager-rollback.html).
 
-# Updating the host with ostree tool
+# Updating the host with OSTree tool
 
 ## OTA updates