Remove ocaml-depext line

I thought I'd done this, but clearly failed to actually commit it!

Author: SquidDev

.github/workflows/build.yml

@@ -31,7 +31,6 @@ jobs:
           uses: windows-latest
           ocaml:
             ocaml-compiler: "5.3.0"
-            opam-depext: false
           input-file: illuaminate.exe
           output-file: illuaminate-windows-x86_64.exe
           dune-flags: