Update to work with never opencv

[JoelSjogren]

stack install -->

opencv                           > [1 of 2] Compiling Main             ( /tmp/stack-63c94d8788603334/opencv-0.0.2.1/Setup.hs, /tmp/stack-63c94d8788603334/opencv-0.0.2.1/.stack-work/dist/x86_64-linux-tinfo6/Cabal-3.2.1.0/setup/Main.o )
opencv                           > [2 of 2] Compiling StackSetupShim   ( /home/joel/.stack/setup-exe-src/setup-shim-mPHDZzAJ.hs, /tmp/stack-63c94d8788603334/opencv-0.0.2.1/.stack-work/dist/x86_64-linux-tinfo6/Cabal-3.2.1.0/setup/StackSetupShim.o )
opencv                           > Linking /tmp/stack-63c94d8788603334/opencv-0.0.2.1/.stack-work/dist/x86_64-linux-tinfo6/Cabal-3.2.1.0/setup/setup ...
opencv                           > Configuring opencv-0.0.2.1...
opencv                           > setup: The pkg-config package 'opencv' version ==3.0.0 || >3.0.0 is required
opencv                           > but it could not be found.
opencv                           > 
Completed 68 action(s).

It seems like pkg-config doesn't work with opencv anymore?
opencv/opencv#13154

box% ipython
Python 3.9.2 (default, Feb 20 2021, 18:40:11) 
Type 'copyright', 'credits' or 'license' for more information
IPython 7.22.0 -- An enhanced Interactive Python. Type '?' for help.

In [1]: import cv2

In [2]: cv2.__version__
Out[2]: '4.5.2'