ci: get flutter deps

Author: yukibtc

.github/workflows/precompiled_binaries.yml

@@ -33,6 +33,9 @@ jobs:
         if: (matrix.os == 'ubuntu-20.04')
         run: sdkmanager --install "ndk;25.1.8937393"
 
+      - name: Get flutter deps
+        run: flutter pub get
+
       - name: Precompile
         if: (matrix.os == 'macOS-latest') || (matrix.os == 'windows-latest')
         run: dart run build_tool precompile-binaries -v --manifest-dir=../../rust --repository=rust-nostr/nostr-sdk-flutter