fix(tests): pin prism version

Author: RobertCraigie

scripts/mock

@@ -21,7 +21,7 @@ echo "==> Starting mock server with URL ${URL}"
 
 # Run prism mock on the given spec
 if [ "$1" == "--daemon" ]; then
-  npm exec --package=@stoplight/prism-cli@~5.8 -- prism mock "$URL" &> .prism.log &
+  npm exec --package=@stoplight/[email protected].2 -- prism mock "$URL" &> .prism.log &
 
   # Wait for server to come online
   echo -n "Waiting for server"