Test an upper bound on doctest to solve #7493

Signed-off-by: Mihai Maruseac <mihai.maruseac@gmail.com>

build-constraints.yaml

@@ -1233,7 +1233,7 @@ packages:
         - hspec-wai-json
         - aeson-qq
         - interpolate
-        - doctest
+        - doctest < 0.22.7  # build cycle with 0.22.7: https://github.com/commercialhaskell/stackage/issues/7493
         - base-compat
 
     "Mario Blazevic <blamario@protonmail.com> @blamario":