[test] Revert to using mutable tag for setup-ruby action

While more secure to work on specific SHAs, there are too many manual steps to track to know if a new jruby version is included (ruby-build needs PR merged and release, setup-ruby's bot needs to pick that up, create PR, then a new release created, then dependabot notice the new action and PR created here, then to be merged across branches)

Given the required trust of the ruby ecosystem and same maintainers being involved, it's probably OK to use a mutable tag here.

(cherry picked from commit f5e210e)

Author: chadlwilson

.github/workflows/maven.yml

@@ -86,7 +86,7 @@ jobs:
           cache: maven
 
       - name: Setup JRuby
-        uses: ruby/setup-ruby@829114fc20da43a41d27359103ec7a63020954d4 # v1.255.0
+        uses: ruby/setup-ruby@v1
         with:
           ruby-version: jruby-${{ matrix.jruby_version }}
           bundler-cache: 'false' # Need to install later so we can vary from Gemfile.lock as required for JRuby version compatibility