build: Use flutter version from pubspec.yaml instead of env file

.github/workflows/main_deploy.yaml

@@ -15,10 +15,9 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v6
-      - run: cat .github/workflows/versions.env >> $GITHUB_ENV
       - uses: subosito/flutter-action@v2
         with:
-          flutter-version: ${{ env.FLUTTER_VERSION }}
+          flutter-version-file: pubspec.yaml
       - uses: moonrepo/setup-rust@v1
       - run: rustup component add rust-src --toolchain nightly-x86_64-unknown-linux-gnu
       - name: Prepare web
@@ -40,14 +39,9 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v6
-      - run: cat .github/workflows/versions.env >> $GITHUB_ENV
-      - uses: actions/setup-java@v5
-        with:
-          java-version: ${{ env.JAVA_VERSION }}
-          distribution: 'zulu'
       - uses: subosito/flutter-action@v2
         with:
-          flutter-version: ${{ env.FLUTTER_VERSION }}
+          flutter-version-file: pubspec.yaml
           cache: true
       - name: Set up Ruby
         uses: ruby/setup-ruby@v1