[Fix] Vectorisation of Abs

When an abs function is encountered the Vector printer checks if its argument is a 'VectorMemoryAccess'. This causes two issues 1. only abs functions containing a field access can be vectorised and 2. even worse, if the abs function does not contain a 'VectorMemoryAccess' the scalar version is printed which causes faulty code.

This MR simply removes the condition.

src/pystencils/backends/cbackend.py

@@ -614,7 +614,7 @@ class VectorizedCustomSympyPrinter(CustomSympyPrinter):
             return None
 
     def _print_Abs(self, expr):
-        if 'abs' in self.instruction_set and isinstance(expr.args[0], VectorMemoryAccess):
+        if 'abs' in self.instruction_set:
             return self.instruction_set['abs'].format(self._print(expr.args[0]), **self._kwargs)
         return super()._print_Abs(expr)