Update bash script to run Knapsack Pro

We made a few experiments with forked repositeries after applying commit
dc1e0209a and everything seems to work fine, but it looks like that
isn't the case. For instance, on pull requests opened by external
contributors, the tests aren't running.

The fix we're applying is mentioned on the Knapsack Pro repository [1]
(pull request 197).

[1] https://github.com/KnapsackPro/knapsack_pro-ruby

bin/knapsack_pro_rspec

@@ -3,8 +3,8 @@ if [ "$KNAPSACK_PRO_TEST_SUITE_TOKEN_RSPEC" = "" ]; then
   KNAPSACK_PRO_ENDPOINT=https://api-disabled-for-fork.knapsackpro.com \
     KNAPSACK_PRO_TEST_SUITE_TOKEN_RSPEC=disabled-for-fork \
     KNAPSACK_PRO_MAX_REQUEST_RETRIES=0 \
-    bundle exec rake knapsack_pro:rspec # use Regular Mode here always
+    KNAPSACK_PRO_CI_NODE_RETRY_COUNT=0 \
+    bundle exec rake knapsack_pro:queue:rspec
 else
-  # Queue Mode - dynamic tests allocation across CI nodes
   bundle exec rake knapsack_pro:queue:rspec
 fi