fix: logical prefixed not fails GitHub workflow syntax

[maxrake]

It turns out the following syntax is invalid for a GitHub Actions workflow:

# both of these forms fail the syntax check
if: ! contains(github.ref, 'rc')
if: !contains(github.ref, 'rc')

This was discovered after merging the new Docker workflow and attempting to trigger it

After searching the docs and coming up empty, a GitHub Community Forum post for this issue (but for startswith instead of contains) showed the way to go:

# it works if you enclose everything in double quotes
if: "!contains(github.ref, 'rc')"

# this also works and reads more cleanly to my eye
if: contains(github.ref, 'rc') != true

Closes #50

Checklist

• Does this PR have an associated issue (i.e., closes #<issueNum> in description above)?
• Have you ensured that you have met the expected acceptance criteria?
• Have you created sufficient tests?
• Have you updated all affected documentation?

[maxrake]

The changes made in the most recent commit have been tested and confirmed to work...at least syntactically. Confirmation on the ability to trigger the repository_dispatch workflow still won't be possible until the changes here make it into the default (e.g., main) branch.