Update the CI actions to their current majors

checkout v4 to v7, setup-python v5 to v7, cache v4 to v6, upload-artifact v4
to v7. All four majors are ESM and Node 24 runtime migrations; none of the
inputs used here changed. upload-artifact v6 onwards needs a runner of at
least 2.327.1, which the GitHub hosted runners satisfy.

Author: caveman99

.github/workflows/build.yml

@@ -17,12 +17,12 @@ jobs:
       matrix:
         env: [native, native-meshtastic-modes]
     steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-python@v5
+      - uses: actions/checkout@v7
+      - uses: actions/setup-python@v7
         with:
           python-version: "3.x"
       - name: Cache PlatformIO
-        uses: actions/cache@v4
+        uses: actions/cache@v6
         with:
           path: ~/.platformio
           key: pio-${{ runner.os }}-${{ hashFiles('**/platformio.ini') }}
@@ -49,12 +49,12 @@ jobs:
             dir: tools/nrf52_codebook_flash
             env: t-echo-card
     steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-python@v5
+      - uses: actions/checkout@v7
+      - uses: actions/setup-python@v7
         with:
           python-version: "3.x"
       - name: Cache PlatformIO
-        uses: actions/cache@v4
+        uses: actions/cache@v6
         with:
           path: ~/.platformio
           key: pio-${{ runner.os }}-${{ matrix.env }}-${{ hashFiles('**/platformio.ini') }}
@@ -70,7 +70,7 @@ jobs:
         run: pio run -e ${{ matrix.env }}
         working-directory: ${{ matrix.dir }}
 
-      - uses: actions/upload-artifact@v4
+      - uses: actions/upload-artifact@v7
         with:
           name: ${{ matrix.name }}
           if-no-files-found: error