chore: [SEC-7924] pin third-party GitHub Actions to commit SHAs (#452)

## Summary

Pin all third-party GitHub Actions to full-length commit SHAs to prevent
supply chain attacks.

Addresses findings from the
[`third-party-action-not-pinned-to-commit-sha`](https://github.com/launchdarkly/semgrep-rules/blob/main/github-actions/third-party-action-not-pinned-to-commit-sha.yml)
Semgrep rule.

## Test plan

- [ ] Verify CI passes with pinned action SHAs
<!-- ld-jira-link -->
---
Related Jira issue: [SEC-7924: Unpinned GitHub Actions
remediation](https://launchdarkly.atlassian.net/browse/SEC-7924)
<!-- end-ld-jira-link -->

Author: pkaeding

.github/actions/publish-ruby-sdk/action.yml

@@ -34,7 +34,7 @@ runs:
           uses: actions/checkout@v4
 
         - name: Install Ruby
-          uses: ruby/setup-ruby@v1
+          uses: ruby/setup-ruby@3ff19f5e2baf30647122352b96108b1fbe250c64 # v1
           with:
               ruby-version: ${{ inputs.ruby-version }}
               bundler-cache: true

.github/workflows/ruby-plugin.yml

@@ -28,7 +28,7 @@ jobs:
               with:
                   token: ${{ secrets.GITHUB_TOKEN }}
             - name: Install Ruby
-              uses: ruby/setup-ruby@v1
+              uses: ruby/setup-ruby@3ff19f5e2baf30647122352b96108b1fbe250c64 # v1
               with:
                   ruby-version: ${{ matrix.ruby }}
                   bundler-cache: true
@@ -53,7 +53,7 @@ jobs:
               with:
                   token: ${{ secrets.GITHUB_TOKEN }}
             - name: Install Ruby
-              uses: ruby/setup-ruby@v1
+              uses: ruby/setup-ruby@3ff19f5e2baf30647122352b96108b1fbe250c64 # v1
               with:
                   ruby-version: '3.3'
                   bundler-cache: true
@@ -74,7 +74,7 @@ jobs:
               with:
                   token: ${{ secrets.GITHUB_TOKEN }}
             - name: Install Ruby
-              uses: ruby/setup-ruby@v1
+              uses: ruby/setup-ruby@3ff19f5e2baf30647122352b96108b1fbe250c64 # v1
               with:
                   ruby-version: '3.3'
                   bundler-cache: true