[pygobject] examples: Fix flake8 whitespace error

[Nirbheek Chauhan <nirbheekc src gnome org>]

commit 17a6d85c259e3b98725cb6dcc34c77a9659fd3bf
Author: Nirbheek Chauhan <nirbheek centricular com>
Date:   Sun Jul 31 16:08:01 2022 +0530

    examples: Fix flake8 whitespace error
    
    + python -m flake8
    ./examples/demo/demos/combobox.py:212:24: E275 missing whitespace after keyword

 examples/demo/demos/combobox.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/examples/demo/demos/combobox.py b/examples/demo/demos/combobox.py
index 36034bac..1215f16c 100644
--- a/examples/demo/demos/combobox.py
+++ b/examples/demo/demos/combobox.py
@@ -209,7 +209,7 @@ class ComboboxApp:
         path = tree_model.get_path(treeiter)
         indices = path.get_indices()
 
-        sensitive = not(indices[0] == 1)
+        sensitive = not (indices[0] == 1)
 
         cell.set_property('sensitive', sensitive)