[libadwaita] docs: Fix a few copy-paste errors in ButtonContent

[Alexander Mikhaylenko <alexm src gnome org>]

commit 3b5e42272379cb8e3d8d165747f5884461c8ba37
Author: Jonas Dreßler <verdre v0yd nl>
Date:   Wed Feb 9 07:03:37 2022 +0100

    docs: Fix a few copy-paste errors in ButtonContent

 src/adw-button-content.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/src/adw-button-content.c b/src/adw-button-content.c
index 4889a3fd..07c94bf4 100644
--- a/src/adw-button-content.c
+++ b/src/adw-button-content.c
@@ -51,7 +51,7 @@
  * ╰── label
  * ```
  *
- * `AdwSplitButton`'s CSS node is called `buttoncontent`. It contains the
+ * `AdwButtonContent`'s CSS node is called `buttoncontent`. It contains the
  * subnodes `image` and `label`.
  *
  * When inside a `GtkButton` or `AdwSplitButton`, the button will receive the
@@ -60,7 +60,7 @@
  *
  * ## Accessibility
  *
- * `AdwSplitButton` uses the `GTK_ACCESSIBLE_ROLE_GROUP` role.
+ * `AdwButtonContent` uses the `GTK_ACCESSIBLE_ROLE_GROUP` role.
  *
  * Since: 1.0
  */