Try to correct interpretation of cache-read-only

Author: wilkinsona

.github/actions/prepare-gradle-build/action.yml

@@ -42,7 +42,7 @@ runs:
     - name: Set Up Gradle
       uses: gradle/actions/setup-gradle@d156388eb19639ec20ade50009f3d199ce1e2808 # v4.1.0
       with:
-        cache-read-only: ${{ inputs.cache-read-only }}
+        cache-read-only: ${{ inputs.cache-read-only == 'true' }}
         develocity-access-key: ${{ inputs.develocity-access-key }}
     - name: Configure Gradle Properties
       shell: bash