Log Message:
ocaml-lablgtk3: update to 3.1.5.

## In Lablgtk-3.1.5

2024.06.10 [Jacques]
  * Prepare for release
  * Fix typos in README.md (#182) [Sylvain Chiron]

2024.05.20 [Jacques]
  * Typo in ml_gtk_text_buffer_get_iter_at_line_index. (#181) [Hugo Herbelin]

2024.05.14 [Jacques]
  * Support windows sockets in Glib.IO.channel_of_descr (#176)
    [with Michael Soegtrop]

2024.03.24 [Jacques]
  * fix pointer incompatibility in ml_gtk_style_context_list_classes (#178)

## In Lablgtk-3.1.4

2024.01.31 [Jacques]
  * use Bytes rather than String
  * Various missing bindings, including lablgtk3-rsvg2 (#128)
  * GtkStyleContext: Add missing class and provider functions (#163)
  * Add GdkEvent.Scroll.delta_{x,y} (#173) [Thomas Leonard]