Update int.cloudbuild.yaml

Author: apeabody

build/int.cloudbuild.yaml

@@ -38,7 +38,7 @@ steps:
       _INFRA_FOLDERS="build test .github"
       while read d; do
         echo "${d%/}"
-        if [[ "${_INFRA_FOLDERS}" =~ "${d%/}" ]]; then
+        if [[ "${_INFRA_FOLDERS}" =~ ${d%/} ]]; then
           echo "Infrastructure folder ${d%/} has changed; no tests will be pruned."
           exit 0 # do not prune
         fi