ci: bump actions/checkout and actions/setup-python to v7 (Node 24)

Clears the 'Node 20 is being deprecated' warnings by moving the actions
we pin to their current Node 24 majors (both released 2026-07-20).
hassfest@master and hacs/action@main are third-party and float on their
own branches.

.github/workflows/validate.yml

@@ -19,7 +19,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout the repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v7
 
       - name: Run hassfest validation
         uses: home-assistant/actions/hassfest@master
@@ -29,7 +29,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout the repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v7
 
       - name: Run HACS validation
         uses: hacs/action@main
@@ -41,10 +41,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout the repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v7
 
       - name: Set up Python
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@v7
         with:
           python-version: "3.14"