Bump checkout actions to v4 for Node20

Author: gbfredrik

.github/workflows/build_windows.yaml

@@ -35,7 +35,7 @@ jobs:
             platform: x64
             boost-lib: 64
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: get QuantLib
       run: |
         git submodule update --init

.github/workflows/linux_build.yaml

@@ -26,7 +26,7 @@ jobs:
     name: building
     runs-on: ubuntu-22.04
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: get QuantLib
       run: |
         git submodule update --init

.github/workflows/macos_ARM64_build.yaml

@@ -25,7 +25,7 @@ jobs:
   build:
     runs-on: macos-11
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: get QuantLib
       run: |
         git submodule update --init