CI config: bump actions versions (#350)

this should make GitHub stop complaining that we're running
old Node 16 based actions

Author: SethTisue

.github/workflows/validate.yml

@@ -23,12 +23,12 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0
 
       - name: Set up JDK ${{matrix.java}}
-        uses: actions/setup-java@v2
+        uses: actions/setup-java@v4
         with:
           distribution: temurin
           java-version: ${{matrix.java}}
@@ -47,12 +47,12 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0
 
       - name: Set up JDK 8
-        uses: actions/setup-java@v2
+        uses: actions/setup-java@v4
         with:
           distribution: temurin
           java-version: 8