build: fix step name in GitHub Actions workflow

The CI workflow doesn't use the matrix strategy so there is no
`${{ matrix.node-version }}` variable to use in the `Use Node.js`
step names.

PR-URL: nodejs#31323
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Jiawen Geng <technicalcute@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

.github/workflows/CI.yml

@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
-      - name: Use Node.js ${{ matrix.node-version }}
+      - name: Use Node.js 13
         uses: actions/setup-node@v1
         with:
           node-version: 13.x
@@ -19,7 +19,7 @@ jobs:
     runs-on: windows-latest
     steps:
       - uses: actions/checkout@v2
-      - name: Use Node.js ${{ matrix.node-version }}
+      - name: Use Node.js 13
         uses: actions/setup-node@v1
         with:
           node-version: 13.x
@@ -33,7 +33,7 @@ jobs:
     runs-on: macOS-latest
     steps:
       - uses: actions/checkout@v2
-      - name: Use Node.js ${{ matrix.node-version }}
+      - name: Use Node.js 13
         uses: actions/setup-node@v1
         with:
           node-version: 13.x
@@ -45,7 +45,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v2
-    - name: Use Node.js ${{ matrix.node-version }}
+    - name: Use Node.js 10
       uses: actions/setup-node@v1
       with:
         node-version: 10.x
@@ -61,7 +61,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v2
-    - name: Use Node.js ${{ matrix.node-version }}
+    - name: Use Node.js 10
       uses: actions/setup-node@v1
       with:
         node-version: 10.x
@@ -71,7 +71,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v2
-    - name: Use Node.js ${{ matrix.node-version }}
+    - name: Use Node.js 10
       uses: actions/setup-node@v1
       with:
         node-version: 10.x