entry: Update CSS node docs

Remove all the nodes that are subnodes of GtkText nowadays and refer to
the GtkText docs instead.

gtk/gtkentry.c

@@ -124,13 +124,9 @@
  * |[<!-- language="plain" -->
  * entry[.flat][.warning][.error]
  * ├── text[.readonly]
- * ├── placeholder
  * ├── image.left
  * ├── image.right
- * ├── [selection]
- * ├── [block-cursor]
  * ├── [progress[.pulse]]
- * ╰── [window.popup]
  * ]|
  *
  * GtkEntry has a main node with the name entry. Depending on the properties
@@ -140,25 +136,11 @@
  * When the entry shows icons, it adds subnodes with the name image and the
  * style class .left or .right, depending on where the icon appears.
  *
- * When the entry has a selection, it adds a subnode with the name selection.
- *
- * When the entry is in overwrite mode, it adds a subnode with the name block-cursor
- * that determines how the block cursor is drawn.
- *
  * When the entry shows progress, it adds a subnode with the name progress.
  * The node has the style class .pulse when the shown progress is pulsing.
  *
- * The CSS node for a context menu is added as a subnode below entry as well.
- *
- * The undershoot nodes are used to draw the underflow indication when content
- * is scrolled out of view. These nodes get the .left and .right style classes
- * added depending on where the indication is drawn.
- *
- * When touch is used and touch selection handles are shown, they are using
- * CSS nodes with name cursor-handle. They get the .top or .bottom style class
- * depending on where they are shown in relation to the selection. If there is
- * just a single handle for the text cursor, it gets the style class
- * .insertion-cursor.
+ * For all the subnodes added to the text node in various situations,
+ * see #GtkText.
  */
 
 #define NAT_ENTRY_WIDTH  150