.github/workflows: update to newer versions of the actions

The v2 versions are considered deprecated by Github.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

.github/workflows/buildroot-external-st.yml

@@ -6,10 +6,10 @@ jobs:
       matrix:
         config: [ st_stm32mp157a_dk1_defconfig, st_stm32mp157a_dk1_demo_defconfig, st_stm32mp157d_dk1_defconfig, st_stm32mp157d_dk1_demo_defconfig, st_stm32mp157c_dk2_defconfig, st_stm32mp157c_dk2_demo_defconfig, st_stm32mp157f_dk2_defconfig, st_stm32mp157f_dk2_demo_defconfig, st_stm32mp135f_dk_defconfig, st_stm32mp135f_dk_demo_defconfig ]
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
         with:
           path: buildroot-external-st
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
         with:
           repository: bootlin/buildroot
           ref: st/2023.02.2
@@ -23,7 +23,7 @@ jobs:
       - name: Compress sdcard.img
         run: gzip -9 output/images/sdcard.img
       - name: Store images
-        uses: actions/upload-artifact@v2
+        uses: actions/upload-artifact@v3
         with:
           name: image-${{ matrix.config }}
           path: output/images/sdcard.img.gz