doc fix: remove extra 'we' in designdecisions (#4199)

docs/src/DeveloperDocumentation/design_decisions.md

@@ -90,7 +90,7 @@ software frameworks on a lower level:
  - Gap
 
 So: Please use it. It is safe to assume all can be improved, however, if we try
-to perfect every single line of code again and again, we we won't get anywhere;
+to perfect every single line of code again and again, we won't get anywhere;
 there is a balance to be found.
 For preference: 
 ```