Exclude Pulley from MIRI testing on PRs

This hasn't actually turned up anything in quite some time and MIRI
testing is relatively slow so by default don't test MIRI on Pulley PRs
(it's of course still tested on the merge queue though)

.github/workflows/main.yml

@@ -239,7 +239,6 @@ jobs:
           fi
           if grep -q pulley names.log; then
             echo test-nightly=true >> $GITHUB_OUTPUT
-            echo test-miri=true >> $GITHUB_OUTPUT
           fi
         fi
         matrix="$(node ./ci/build-test-matrix.js ./commits.log ./names.log $run_full)"