[FIX] view: Fix a type error with PyQt6

[ales-erjavec]

Issue

Using pinch gesture on the canvas when using PyQt6 causes an error

----------------------------------------------------------------------
Traceback (most recent call last):
 ...
  File "/home/ales/devel/orange-canvas-core/orangecanvas/canvas/view.py", line 199, in __setZoomLevel
    self.centerOn(anchor + diff)
                  ~~~~~~~^~~~~~
TypeError: unsupported operand type(s) for +: 'QPoint' and 'QPointF'

----------------------------------------------------------------------

Changes

Cast the anchor to QPointF

[codecov-commenter]

Codecov Report

All modified lines are covered by tests ✅

Comparison is base (636c6b3) 75.49% compared to head (9ca81e3) 75.51%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #285      +/-   ##
==========================================
+ Coverage   75.49%   75.51%   +0.01%     
==========================================
  Files          99       99              
  Lines       21043    21043              
==========================================
+ Hits        15886    15890       +4     
+ Misses       5157     5153       -4     

Files	Coverage Δ
orangecanvas/canvas/view.py	50.27% <100.00%> (+2.18%)	⬆️

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