Update flutter-build.yml (#15454)

.github/workflows/flutter-build.yml

@@ -1984,6 +1984,7 @@ jobs:
           sudo apt-get install -y libarchive-tools libfuse2
           # set-up appimage-builder
           # https://github.com/AppImage/AppImageKit/issues/1395
+          sudo pip3 install "setuptools_scm<10"
           sudo pip3 install git+https://github.com/rustdesk-org/appimage-builder.git
           # run appimage-builder
           pushd appimage