Fix Lint bash failure when a .sh script is in the PR patch

[fmichaelobrien]

Update 20231124: thank Alain, it looks like both repos are aligned but with different severity settings - I rechecked tools after your verify.
I will fix the info level warnings before modifying the linter filter.

Update: Looks like an issue with the BASH linter
There currently are no .sh files in the main repo - so any repo without a .sh or .bash will pass

For example the following PR does not contain a .sh script so the section where .sh/.bash scripts are gathered is skipped
https://github.com/GoogleCloudPlatform/pubsec-declarative-toolkit/actions/runs/6973355149/job/18977199193?pr=724#step:5:86

The following PR does return the first sh script of the pdt repo and fails even when all the errors and warnings are fixed and we are left with only INFO level outputs.

https://github.com/GoogleCloudPlatform/pubsec-declarative-toolkit/actions/runs/6973900937/job/18978709528?pr=612#step:5:89

The lint level is set at info

          SHELLCHECK_OPTS: "--severity=info"

Our other repos where we do have scripts do not run the bash linter
ssc-spc-ccoe-cei/gcp-tools#64
ssc-spc-ccoe-cei/gcp-tools#53

parking for now - will fix the linter after #446

[fmichaelobrien]

I'll test .github modifications around the bash linter - out of band on my private fork first over the WE