octave: build without qscintilla by default

- qscintilla is used for IDE features in the GUI, which is not built since qt support isn't enabled
- this removes qt from the Octave closure

pkgs/top-level/all-packages.nix

@@ -9205,6 +9205,7 @@ in
     let
       defaultOctaveOptions = {
         qt = null;
+        qscintilla = null;
         ghostscript = null;
         graphicsmagick = null;
         llvm = null;
@@ -9226,6 +9227,7 @@ in
 
   octaveFull = (lowPrio (octave.override {
     qt = qt4;
+    inherit qscintilla;
     overridePlatforms = ["x86_64-linux" "x86_64-darwin"];
     openblas = if stdenv.isDarwin then openblasCompat else openblas;
   }));