lint howto/upgrades

Turns out we had an HTML syntax error! Imagine that.

Also, that long heading was weird anyways.

howto/upgrades.md

@@ -17,6 +17,7 @@ The above graphic shows the progress of the migration between major
 releases. It can be regenerated with the [predict-os](https://gitlab.com/anarcat/predict-os) script. It
 pulls information from [howto/puppet](howto/puppet) to update a [CSV file](data.csv) to
 keep track of progress over time.
+</figcaption>
 </figure>
 
 ### Team-specific upgrade policies
@@ -182,8 +183,8 @@ LDAP hosts have information about how they can be rebooted, in the
 
 ### Example runs
 
-#### This documenation is now deprecated as we are now using unattended-upgrades
-#### and needrestart
+**This documenation is now deprecated as we are now using
+unattended-upgrades and needrestart.**
 
 Here's an example run of the upgrade tool: