fix a typo that broke a link within new documentation

docs/Extending-Models.md

@@ -1,6 +1,6 @@
 # Extending and Customizing Oxidized Models
 
-Oxidized supports a growing list of [operating system types](Supported-Os-Types.md). Out of the box, most model implementations collect configuration data. Some implementations also include a conservative set of additional commands that collect basic device information (device make and model, software version, licensing information, ...) which are appended to the configuration as comments.
+Oxidized supports a growing list of [operating system types](Supported-OS-Types.md). Out of the box, most model implementations collect configuration data. Some implementations also include a conservative set of additional commands that collect basic device information (device make and model, software version, licensing information, ...) which are appended to the configuration as comments.
 
 A user may wish to extend an existing model to collect the output of additional commands. Oxidized offers smart loading of models in order to facilitate this with ease, without the need to introduce changes to the upstream source code.