docs: Use code for class names in links

So that they fit with the documentation guidelines, and with the links
generated by gi-docgen.

docs/reference/glib/datalist-and-dataset.md

@@ -14,7 +14,7 @@ The [type@GLib.Quark] methods are quicker, since the strings have to be
 converted to [type@GLib.Quark]s anyway.
 
 Data lists are used for associating arbitrary data with
-[GObject](../gobject/class.Object.html)s, using [`g_object_set_data()`](../gobject/method.Object.set_data.html) and related
+[`GObject`](../gobject/class.Object.html)s, using [`g_object_set_data()`](../gobject/method.Object.set_data.html) and related
 functions. The data is stored inside opaque [type@GLib.Data] elements.
 
 To create a datalist, use [func@GLib.datalist_init].

docs/reference/glib/file-utils.md

@@ -5,8 +5,8 @@ SPDX-FileCopyrightText: 2012 Dan Winship
 # File Utilities
 
 Do not use these APIs unless you are porting a POSIX application to Windows.
-A more high-level file access API is provided as GIO — see the documentation
-for [GFile](../gio/iface.File.html).
+A more high-level file access API is provided as GIO; see the documentation
+for [`GFile`](../gio/iface.File.html).
 
 ## POSIX File Wrappers
 

docs/reference/glib/spawn.md

@@ -15,8 +15,8 @@ and asynchronous variants ([func@GLib.spawn_async],
 complete shell-like command line ([func@GLib.spawn_command_line_sync],
 [func@GLib.spawn_command_line_async]).
 
-See [GSubprocess](../gio/class.Subprocess.html) in GIO for a higher-level API that provides
-stream interfaces for communication with child processes.
+See [`GSubprocess`](../gio/class.Subprocess.html) in GIO for a higher-level API
+that provides stream interfaces for communication with child processes.
 
 An example of using [func@GLib.spawn_async_with_pipes]:
 ```c