ci: migrate actions to v5 (checkout, setup-java, upload-artifact)

Fixes Node.js 20 deprecation warnings on GitHub Actions runners.

.github/workflows/build.yml

@@ -27,8 +27,8 @@ jobs:
           - { mc: "26.1.2",  coordinate: "io.papermc.paper:paper-api:26.1.2.build.74-stable", java: 25, release: 25, api: "1.21" }
           - { mc: "26.2",    coordinate: "io.papermc.paper:paper-api:26.2.build.97-stable",   java: 25, release: 25, api: "1.21" }
     steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-java@v4
+      - uses: actions/checkout@v5
+      - uses: actions/setup-java@v5
         with:
           distribution: temurin
           java-version: ${{ matrix.java }}
@@ -40,7 +40,7 @@ jobs:
           -PjavaRelease=${{ matrix.release }}
           -PapiVersion=${{ matrix.api }}
       - name: Upload jar
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v5
         with:
           name: LoParkour-${{ matrix.mc }}
           path: build/libs/LoParkour-*.jar
@@ -50,15 +50,15 @@ jobs:
     name: Quality gate (default 1.20.4)
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-java@v4
+      - uses: actions/checkout@v5
+      - uses: actions/setup-java@v5
         with:
           distribution: temurin
           java-version: 21
       - name: Full build
         run: ./gradlew --no-daemon build
       - name: Upload default jar
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v5
         with:
           name: LoParkour-default-1.20.4
           path: build/libs/LoParkour-*.jar