Installer: Fix double escaping of config-download-localsettings.

The link was outputted as:
 "Download &lt;code&gt;LocalSettings.php&lt;/code&gt;"
rendered as:
 "Download <code>LocalSettings.php</code>"
screenshot:
 http://cl.ly/image/1y2O3y2S2B19

Change-Id: I55a677b2a0f83dc6627d712584b8faa00e413b8b
Follows-up: Iaa2c89d6
Bug: 44526
Merge "Installer: Fix double escaping of config-download-localsettings."