fixup handler docstring

Author: half-duplex

sopel/plugins/handlers.py

@@ -114,7 +114,7 @@ def get_meta_description(self):
         * type: the plugin's type
         * source: the plugin's source
           (filesystem path, python import path, etc.)
-        * version: the plugin's version string if available, otherwise `None`
+        * version: the plugin's version string if available, otherwise ``None``
         """
         raise NotImplementedError
 
@@ -271,7 +271,7 @@ def get_meta_description(self):
         * label: see :meth:`~sopel.plugins.handlers.PyModulePlugin.get_label`
         * type: see :attr:`PLUGIN_TYPE`
         * source: the name of the plugin's module
-        * version: the version string of the plugin if available, otherwise `None`
+        * version: the version string of the plugin if available, otherwise ``None``
 
         Example::