Add Node.js version to Gutenberg testing.

Also test sending no `node` input.

.github/workflows/callable-test-gutenberg-build-process.yml

@@ -16,6 +16,11 @@ on:
         required: false
         type: 'string'
         default: 'src'
+      node:
+        description: 'The version of Node.js to test'
+        required: false
+        type: 'string'
+        default: ''
 
 env:
   GUTENBERG_DIRECTORY: ${{ inputs.directory == 'build' && 'build' || 'src' }}/wp-content/plugins/gutenberg
@@ -56,6 +61,7 @@ jobs:
       - name: Set up Node.js
         uses: actions/setup-node@5e21ff4d9bc1a8cf6de233a3057d20ec6b3fb69d # v3.8.1
         with:
+          node-version: ${{ inputs.node }}
           node-version-file: '.nvmrc'
           cache: npm
           cache-dependency-path: |

.github/workflows/test-build-processes.yml

@@ -40,7 +40,7 @@ jobs:
       matrix:
         os: [ ubuntu-latest, windows-latest ]
         directory: [ 'src', 'build' ]
-        node: [ '', '18', '20' ]
+        node: [ '18', '20' ]
     with:
       os: ${{ matrix.os }}
       directory: ${{ matrix.directory }}
@@ -65,11 +65,9 @@ jobs:
       matrix:
         os: [ macos-latest ]
         directory: [ 'src', 'build' ]
-        node: [ '18', '20' ]
     with:
       os: ${{ matrix.os }}
       directory: ${{ matrix.directory }}
-      node: ${{ matrix.node }}
 
   # Tests the Gutenberg plugin build process on multiple operating systems when run within a wordpress-develop checkout.
   test-gutenberg-build-process: