tests: add placeholder for function gui_key_paste_finish

tests/unit/gui/test-gui-key.cpp

@@ -1655,6 +1655,16 @@ TEST(GuiKey, PasteStart)
     /* TODO: write tests */
 }
 
+/*
+ * Tests functions:
+ *   gui_key_paste_finish
+ */
+
+TEST(GuiKey, PasteFinish)
+{
+    /* TODO: write tests */
+}
+
 /*
  * Tests functions:
  *   gui_key_get_paste_lines