Merge pull request #218 from jorisdral/jdral/revise-io-sim-1.8

`io-sim-1.8` fails to build with `io-classes-1.7` and earlier versions

Author: coot

io-sim/io-sim.cabal

@@ -66,7 +66,7 @@ library
     default-extensions: GADTs
   build-depends:       base              >=4.16 && <4.22,
                        io-classes:{io-classes,strict-stm,si-timers}
-                                        ^>=1.6 || ^>= 1.7 || ^>= 1.8,
+                                        ^>=1.8,
                        exceptions        >=0.10,
                        containers,
                        deepseq,